Since I haven't made a balance reconciliation statement for seven months, there are many outstanding items. Can the balance of the bank balance reconciliation table be negative after adjustment?

Of course not. Actually, it depends on whether your leader allows it or not.

But it is wrong to do accounting, because there is no negative bank balance. In other words, it's just a joke, which means that your balance reconciliation table has not been adjusted correctly at all. You should adjust it carefully again according to the method given to you upstairs.