The Notice to Keeper (NtK) is required to notify a period of parking, and it does. Within that period of parking they must also allow a minimum grace period of 10 minutes. As the maximum permitted time is 90 minutes, even adding the extra 10 minutes grace period, the driver overstayed by 29 minutes.
So your appeal argument about PoFA 9(2)(a) was misguided. Doesn't really matter though as any initial appeal is always going to be rejected.
Without seeing the actual wording of your POPLA appeal, it is not possible to offer much more advice. You are asking us to respond to the operators evidence pack without seeing exactly what you out in your appeal.
Either way, their NtK is not fully compliant with PoFA, notably 9(2)(e)(i) and 9(2)(a) but not for the reason you gave. The relevant land is not defined. The NtK simply says the contravention occurred at Sainsbury's - Ilford. Is that...
• Sainsbury's 55 Roden St, Ilford IG1 2AA; or
• Sainsbury's King George Ave, Ilford IG2 7SH?
I have had several successful POPLA appeals on this fact, but if you've not included it in the POPLA appeal, then you've thrown that one down the drain.
I wouldn't worry about POPLA. Any unsuccessful decision is not binding on you. All you would have to do is weather a bunch of useless debt recovery letters which you can safely ignore and wait for the inevitable county court claim which, as long as it is defended, even poorly, will eventually be discontinued.
So, either follow the advice here and show us exactly what you put in your POPLA appeal and do a search of POPLA appeals on here where the operators evidence has been rebutted and see what you can come up with.