The original amount of the petty cash fund remained fixed. As cash is disbursed, it is periodically replenished to return the amount of petty cash fund to the original fund balance.
When the petty cash fund custodian sees that the cash balance is getting low, he or she prepares a petty cash replenishment request, attaching the receipts from the cash box and indicating the general ledger account the expenses should be charged to. A standard format could be set up for this petty cash replenishment report.
A check is then made out to the custodian for the amount required to replenish the petty cash fund, and the expenses are recorded.
The custodian (or you as the owner) cashes the check, puts the cash back in the safe or cash box, and the petty cash fund returns to its original amount.