When you save a Bill, you're just recording that you *owe* money--it hasn't left the bank account yet. In accrual recording, the money that you owe is recorded in a liability account called "Accounts Payable."
Liabilities are on the Credit side, so when they increase, they increase to the right.
The expense account "Rent or Lease" has also increased. Expense accounts are on the Debit side, so when they increase, they increase to the left.