As it was explained to me, a slot (or pick, same thing) is for a kid the coach feels he must have. And Nescac allows each school up to 14 of those.
A tip is used for a kid the coach would like to have but he really isnt willing to go all out for the kid.
Of course a tip can turn into a pick if higher recruits go somewhere else. Remember, position, ability and grades all come into play. Sometimes a players grades and package is so good all the coach has to do is use a tip. this is the dance between coaches and admissions.