The system has the limits set. Generally, one can do two in store shops per period, at an unlimited number of stores. (maybe). After that, if one wants to do a third one, it will tell you to email the scheduler.
Some tips: I wanted to do a second shop at a location, but it said to email the scheduler. I moved up my scheduled shop at that location, which then freed up dates and I was able to self-schedule the second one.
In store shops are limited to 4 a day. Try to schedule a fifth, and the system will not let one. Pickups are separate and not counted in the in store daily total. So I could theoretically do 8 shops at day (4 in-store, 4-pick ups).
Do not read so much, look about you and think of what you see there.
Richard Feynman-- letter to Ashok Arora, 4 January 1967, published in Perfectly Reasonable Deviations from the Beaten Track (2005) p. 230