Here goes:

15 Sets. @. 30. =. 450. 25%. Commission. =. $112
Circuit. $200. 15%. Commission =. $. 30

Total monthly recurring commission. =. $142.

1 month SPIFF. $450

Plus. Install $300

This is a average. The more phones the more MRR. Less phones less MRR
Keep in mind, if you don't sell your customers , in most cases someone else will.
Also the more you sell the more MRR you will receive. And also SPIFF can be much larger based on the number of sets .