Right, the idea of using the aggday thing is to solve the problem you mentioned. You want to be able to leave your house 20 times during the day but only have it count once. The aggday setting tells Beeminder how to aggregate the data points for the day. Most goals don’t require you to think about this: you just add up all the data you enter. But for this goal, we want something that will only let you count a single “1” each day, which is why I suggested max or nonzero or binary. (The formulae are listed here: Documentation of aggregation methods would be nice - #4).
I should mention that typically Beeminding isn’t this complicated. I refer to that list of aggday functions about once every two years. So I hope all this doesn’t put a bad taste in your mouth!
Re: premium, I have a suspicion that these nice Beekeeper people might let you have a freebie on the premium plan for this one goal, considering you’re brand new and everybody’s already pitched in this much towards brainstorming how to configure this. But @dreev is probably the person to give an answer here.