What does the following statement mean?

"Late fee becomes due when rent is not received by the end of the 4th day of the rental period."

Does this mean that, for example, if the monthly rental period is from September 1 to September 30, the late fee is due when payment is not received by September 4th?

The same goes for October, correct? That is, the late fee applies for October's rent if payment is not made by October 4th?