There are various type hints for $maxRunTime which indicate it is an int, but this is really a float. Thankfully this hasn't been made an argument type hint so it isn't a php 8.1 compat error.
I think it's more accurate to say that it is commonly (and by default) an int but it could be a float. Or at least, it's usually initially an int for the first job run.
I guess the options are we type hint it as int|float or we ensure it is always cast to a float and type hint accordingly.