is 31623 and 31624 inclusive

Hi Could some one please let me know if 31623 and 31624 are inclusive, when we bill 31623 and 31624, the payers reply that it is inclusive, so we bill it out as 31624 and 31623 - 59. is a 59 modifier really necessary.is that right? please any insight on the above scenario is much appreciated.

Thanks