What functions do real estate statisticians generally use in EXCEL?

I am an accountant of the property management company. In order to calculate the amount of property fees receivable, the balance of prepaid property fees payable and the number of months in arrears for each owner, I have compiled the following formula:

Prepayment balance =DATEDIF(G3, TODAY (), "m")*D3,

Months in arrears =DATEDIF(TODAY (), G3, "m") * D3,

Accounts receivable balance = datedif (G3, today (), "m")+ 1,

Where D3 is the owner's monthly property fee price, G3 is the due date of prepayment, and you only need to enter G3 to get the receivable, prepayment balance and the number of months in arrears.

However, when copying "A/R formula" downwards, there are many identical data, such as 37760.7. At this time, G3 has not entered the year, month and day. If you enter the year, month and day, the work result will be correct. How did this data of 37760.7 come out of thin air? I want to delete it, so that when G3 is empty, the receivable will become "#NUM!" Therefore, the same problem also exists in the replication of the other two formulas.