I hate, hate, hate these shops. If it's the same ones I do, you have to order online, pick up, then complete the mystery shop portion, then leave, then return and return the item you just picked up.
The guidelines have been somewhat corrected. For example, the first one I did, it said to be sure to enter by a different door the second time -- but the location I shopped only had ONE entrance. And they used a lot of jargon initially, which has also been corrected.
And I can NEVER find the right department with the right stuff. Last one, they had me ask a question in Building Materials better asked in garden supplies (and, in fact, the guy in Building Materials told me to go ask in garden supplies! Embarrassing! )
I am always on-site an hour, and the report takes another hour (however, I freely admit I'm very slow on reports: I have a tendency toward perfectionism). YMMV.
By the way, did I mention I really hate these shops?