Commission is sales times the rate
The simplest plan pays a flat percentage of the sales you close: $50,000 at 10 percent is $5,000. The page multiplies the sales figure by the rate and does nothing else, so a plan with no quota is answered in one step and the commissionable line in the table equals the sales line exactly.
Base salary stays on its own line instead of being folded into the commission. That separation is the point of the page: what you earned should mean what your selling produced, and a guaranteed salary is a different fact that does not become larger because you closed a good month.
The total for the period adds the two, and the hero shows both the commission and the total so neither can be mistaken for the other. A zero in the sales field returns zero rather than an error, because a month with no sales is a real, if unwelcome, outcome.
Quotas change which dollars get paid
Many plans pay only on sales above a quota. When a quota is set, the page subtracts it first and applies the rate to the remainder: $50,000 of sales against a $40,000 quota leaves $10,000 commissionable, and at 20 percent that is $2,000 rather than the $10,000 a headline reading might suggest.
The table prints the quota, the commissionable amount and the commission in sequence, so the distance between the headline rate and the money is visible at every step. When the quota sits above the sales, the commissionable line falls to zero and the commission with it - no negative is carried forward.
This is the comparison to make across offers, and the one most people skip. A high rate above an unreachable quota can pay less than a modest rate on every dollar, and the only way to see that is to price both plans at the volume you can actually close.
The rate you feel is the effective one
Across all your sales, the share that actually reaches you is the commission divided by total sales. On the $50,000 book with a 20 percent rate above a $40,000 quota, the effective rate is 4 percent - a fifth of the headline, and the number that describes the offer honestly.
The page prints the effective rate as the last row of the table and repeats it in the summary note, beside the warning about celebrating a headline rate before reading the quota. It is computed from commission alone, with base salary excluded, so it measures the plan rather than your total pay.
Two plans with the same headline rate are rarely the same plan once a quota sits between you and the money. Compare the effective rate first, then read the terms the page deliberately does not model.
The rate is the part you can see
Every other term of a plan lives in the plan document rather than on a calculator. The arithmetic is still worth doing because it turns a rate, a quota and a book of sales into the one figure that says what the plan is worth at your realistic volume, and that figure is often the first honest number in a compensation conversation.
What is not modeled is stated rather than guessed: accelerators above target, clawbacks on refunded or unpaid deals, stepped rates and draws against future commission all need the document itself. If your plan pays on collected revenue rather than bookings, enter the sales you expect to be paid instead of the ones you signed.
The result is an estimate from the numbers you enter, not a promise of earnings and not tax advice. It also leaves out the withholding that comes out of the total later, because take-home pay is a different calculation with a different set of inputs.
Where the plan and the page part ways
A commission page prices a plan exactly as written: sales, a rate, a quota and a base. Real plans add four things arithmetic cannot see - accelerators above 100% of quota, clawbacks when a deal is cancelled or never collected, draws paid against future commission, and splits when two reps work one deal. Each one can move the number by more than the choice between an 8% and a 10% rate, which is why the effective rate is the number to negotiate with and the plan document is the thing to read before signing. Feed the page what the plan actually pays on: collected revenue rather than bookings, if that is how it works.
The counter-example is worth pricing out in full. On a $50,000 book, an 8% plan with no quota pays $4,000 and the effective rate is 8%. A 20% plan with a $60,000 quota pays nothing at all, because the quota sits above the sales and the commissionable line falls to zero. A 20% plan with a $40,000 quota pays $2,000 - half the humble 8% - and the effective rate is 4%. The rate is the headline; the quota decides how much of your book it applies to; the base is the only part you keep in a month with no sales.
Danfio