The National League take a percentage, they call it a levy, which they will take from the net proceeds of the game after all expenses for both clubs (and including the travel and hotel costs for National League board members and officers who attend the match). The remaining proceeds are split 50% each to the 2 clubs.
I tried to find out what percentage they take last season but couldn’t find any info other than it’s agreed with all clubs at the start of the season.