it actually only counts coherent messages and they have to be on top chat for them to count, the more messages you have on top chat the higher the chance of you getting picked for a gift, also you sometimes don't have to be there to receive a gift, if the amount of active chat members is smaller than the amount of gifted memberships the system will just pick subscribers at random and give them a membership even if they're not there when they were gifted, something else if you type a message at the time a gift was given (within 10 or so seconds before or after it's gifted) you have a higher chance to get it than someone else.