After speaking to someone from FNB (thanks for the contact Se@n) who actually had the understanding and took the time to explain, I think I may actually finally understand the eBucks points rule which states "Use between 10% and 90% of your credit limit during the calendar month" in the way FNB intended and apply it.
My misunderstanding of the rule actually relates to the interpretation of the word
"use", which I interpreted as
"spend". I assumed if you have a limit of e.g. R1000, and you
spend between R100 and R900 in the calendar month, you qualify to earn points as per the rule. The rule seems actually to be that you must ensure your
running balance must
at least reach R100 in credit during the calendar month, AND also
not exceed R900 at any point during that calendar month. Seems simple enough, but there are reasons this gets complicated to accurately monitor:
(1) If you do not start from a zero balance at the beginning of the calendar month (e.g. let's say you still have R500 owing on your credit card), you need to make sure you don't make a transaction of more than R400, else you'll immediately be going over that R900 limit for the calendar month. So before you make e.g. that Checkers groceries purchase to the value of R700, you'd need to first transfer R300 into your credit account. Further, it would thus appear that you can spend well above R900 in total on your credit card during the calendar month, so long as you ensure you keep transferring money into your account throughout the month to keep the running balance below R900.
(2) Timing differences between purchase date and transaction post date need to be taken into account, and this is the most difficult factor to manage.
(2a) I'm sure we're all aware of the timing difference between when we make a purchase and when it reflects as a detailed transaction in our account transaction history. The thing that's hard to know is
exactly when it will reflect, and thus exactly what the effect will be on our running balance. One merchant may submit transactions daily, another weekly, so those two transactions made on the same day will post quite a number of days apart.
(2b) Further, non-business days/hours throw a further spanner in the works, and even inter-account transfers (i.e. "topping up" your credit account from your cheque account) will not necessarily (apparently as per FNB) post at the time that you make the transfer.
I know that there are a few ways you can check your remaining available balance after each transaction as a sort of guideline, but at this point it appears FNB are using the running balance as at the actual point in time that each transaction posts. So you pretty much either need to stay quite a bit below that 90% running balance limit or, if you need to get close to and still ensure you don't exceed the limit (e.g. that new game you want to buy costs R900), you need to be patient in between transactions until you actually see the detail of recent transactions reflect in your account to know what that your running balance truly is (and that it's R0 or positive for the purposes of my specific examples).
So right now, I already know I screwed up this particular rule for the current calender month of January 2015

. But I'll try and monitor my spend better next month within these new (to me at least) parameters.