Late fee statement meaning

[Mark Husband-Wood]

Saw this late fee statement on a commercial rent invoice and wondering what it means.

"Late fees: 10% late fee or $300 assessed if this invoice is not paid in full by the 5th of the month."

To me this is not clear if the tenant will be hit with a late fee of 10% or a late fee of $300 dollars.  Am I missing something?

Thanks!