Income $115
Expenses $100
Net income $115 - $100 = $15
to get that you need to enter full income and expenses
or if you just get paid the $15 commission (and your bank account does not see the other) , you need to just enter the $15 commision
Irrespective of the reasons why you would practice Cos-plus accounting (see advantages and disadvantages at Cost plus pricing definition — AccountingTools) Manager does not have equivalent calculation functions of excel in terms of entering a % cost plus.
Also as @Tut says you violate fundamental principles of accounting and most likely illegal under-representing your revenue to your tax authorities when you claim a revenue of only 15 while it should be 115.
Your Revenue/Income is actually for business and tax purposes 115 because that is what the customer pays, see for definition revenue What is revenue? | AccountingCoach. Your direct costs are 100 which results in a gross margin (sometimes called gross profit) of 15. Other expenses such as electricity and labour are subtracted from this gross margin/profit to arrive at a net profit/loss for the business. @Patch explained that you need to enter Income and Expenses (Expenses actually are Direct Costs & Other Expenses) in Manager.