new to rakeback

[UtzChips]

I'm not sure how this works. If I understand it correctly, before I'm eligible for a rakeback, I have to actually put money in the pot.
Then, it's based on what percentage of the pot my money is.
Say I'm getting a 30% rakeback.
If I put $30 into a $90 pot, I've put in 33%.
If the rake was $3.00, I get ($3*.33)*.3 = .297

Next question is: Do they carry forward the 7/10's of a cent and add it onto the next rakeback hand?

Thanks.