I have tried to search the answer but unable to do so

My question goes like this:
I have 2 accounts in 2 different banks and in order to meet the Maintenance Funds requirment, I have to combine these two accounts.
One of the evidence document that I need to provide for maintenance funds is:
Letter from bank confirming funds and that they have been in the bank for at least three months
Since I have accounts in 2 different banks and each account DON'T have 2800GBP alone rather i need to combine both of them to meet the requirement.
So , in this case, I can't get this document from the bank stating that I have the amount in excess of 2800GBP in my account for last 3 months. However, I can get the document stating that I own this account from last 3 months.
Should I clear this point in my Cover Letter for the maintenance fund OR
I would be required to submit some other document as a proof of this.
Please help !
Regards,