It doesn't matter where you are driving during certain peak hours, the incentives calculated are based on 5 in 1 peaks trips per week, you can qualify for incentives as long as >50% peak hour trips done in busy areas.

E.g. You drive for 20 peak hours in a week with mixtures of busy and non busy areas pick-up points, if you've 30 completed jobs in these 20 peak hours, 12 jobs picked up from non busy areas like Puchong and Subang etc.(40%), you are qualified for incentives for the week i.e. you'll received 30 jobs incentives(100%) for that 20 hours because 60% of jobs done in busy areas.

Basically, just think all 5 types of peaks into 1, not calculate hour by hour or types by types, they are accumulated together.  I did keyed in the exact pick-up points addresses to search and count using the busy areas map provided by Grab by comparing to google map using different tab.  So far, the incentives calculated were the exact amounts I got when I did calculations, as well as the percentage.

If you drive Grab from Monday to Wednesday, you'll receive sms reminder regarding percentage on Thursday evening.  If not, you'll receive it on Saturday evening as well.  Anyway, yes Grab always 'spam' you in numerous messages daily.Tried my best to solve your doubt.