Allocating through Statement posting

Hi, I've manually posted bank statement details using Cash Management > Tasks > Statements > 

I use Cheque numbers in the description/reference field and it matches (and allocates) the line to the cheque in the AP module. However last time it also allocated a line posted to a different control account which wasn't intended. This created a difference in a report somewhere which the accountant followed to find this new allocation.

I don't remember doing anything differently and it turns out it would be quite useful if I could replicate this. I could then allocate more lines directly when posting bank statements rather than the accountant allocating it later.

Any help on what I did and how to replicate it much appreciated!