A two day bag limit means your able to keep TWICE the amount of fish you normally can during a single day trip. For example, on a single day trip like a 5,10 or 12 hour trip you can only keep up to 4 grouper aggregate or up to 10 mangrove snapper. On a trip with a two day limit this doubles meaning you can take home up to 8 grouper aggregate or up to 20 mangrove snapper. The trips that offer a two day limit are those trips that are longer than 24 hours meaning only the 39,or  44 hour trips qualify for that two day limit. The 12 hour night trip does NOT get a two day limit, which sometimes people ask about because you leave Friday night and return Saturday. The trip has to be longer than 24 hours (25 hours or longer works) and it has to be on a federally permitted vessel on a charter with a receipt stating that trip is that long and is paid for. On a 39, or 44 hour trip your ticket works as your receipt stating you paid for a trip longer than 24 hours on a federally permitted vessel. On