The current docstring for hexbin has this for mincnt:

mincnt : int > 0, default: *None*
    If not *None*, only display cells with more than *mincnt*
    number of points in the cell.

But, it really displays cells that have more than or equal to mincnt.

The int > 0 is also slightly confusing. It does accept 0 and negative numbers and can appear to relate to the 'more than' below when it does not.