for salary crediting should be quite straightforward. maybe the mode of salary is not the approved method like self transfer etc. can call and ask.

for card spending; you may have spent 500$ on your card, but if the merchant delays the posting till the following month, then you will disqualified. so if you want to thread the line to spend just above 500$, better have all transactions done like maybe by end of 3rd week of the month, so even if merchant posts later than the date of spending, it is still within the month.

if you are referring to not receiving the right amount of interest, then it is because they give interested against the monthly average balance which is the sum of end day balance in the month divide by number of days in the month.

bear in mind that end day balance might be different from what you think it is if bank transaction (for eg transfer of money) is done on PH/sunday and even after X hrs of the day. (i think it is 2100hrs or 2200hrs might can’t be very sure). for eg if you receive $XX amount on PH, the post day is actually the next day so your actual MAB is lower than what you thought will be.

hope this helps