If you have worked out a different rate for your sitter other than what they have posted in their profile, you can make that change in the payment process.

After you stop the timer and tap “Pay Sitter”, the next screen asks you to confirm the time and rate for which you would like to pay the sitter. Change the rate by tapping the “Base Rate” field and entering a new rate. When you continue through the payment process, it will calculate the amount due based on the adjusted rate.