Question

So i was having a bit of trouble with PL/SQL.
in this paragraph.

PROCEDURE pay_out_balance (
account_id_in IN accounts.id%TYPE)
IS
1_balance_remaining NUMBER;
BEGIN
LOOP
1_balance_remaining := account_balance (account_id_in);

IF 1_balance_remaining <1000
THEN
EXIT:
ELSE
apply_balance (account_id_in, 1_balance_remaining);
END IF;
END LOOP;
END pay_out_balance;

why does the statement 1_balance_remaining NUMBER;

Have that number 1 infront of it, does it have to do with the line number or the account number or something else?
could anyone help meout