Could you write the syntax (code) that is leading to this warning? Probably it is a definition of a set. If you double-click on the warning, it will indicate to you the code line that is incorrect.
Maybe you can try using the funcion val(Parameter) to solve it, as the warning message already suggested.
as the message suggested, you may search "warning_lag_lead_on_subset_of_integers" in the option dialog and check the meaning. Basically, it wants to make you aware when the subset is like
i in {1, 3,5}
if i =1, lead on the subset will be i+1 = 3 , while as an integer, i+1=2.
