Pending balance transaction affecting available balance

I am still confused about the query i made this morning with regard to my ledger balance vs a transaction that was pending and instead of a reduction in the ledger balance it became a reduction in my available balance.

On the 1st of January i had an available balance of R14279. I made a purchase of R489 from surf4life and my available balance was R13790 after the transaction however this became a pending transaction on the system which formed the total of the legder balance. So in essence my pending transactions + my available balance = my ledger balance which i understand fully. So after the transaction the R489 was deducted from my account available balance R14279- R489= R13790 and added as part of the ledger balance meaning that when the transaction clears from the vendor it would only affect my ledger balance as it had been provisioned for by being subtracted from the available balance but included on the ledger balance.

However this morning as the transaction cleared i had an available balance of R9000 not sure what my ledger balance was with the outstanding transactions but instead of the R489 payment for surf4life reducing my ledger balance as it was provisioned for at the time of the transaction it made a deduction from my available balance which is a double transaction

I have images for reference to the transaction so a further investigation in this regard to be done as this could have been a system error not yet identified and if it could be rectified before it affects a lot more customers

Your comprehensive feedback in this regard will be greatly appreciated