I apologize. I will try to clarify. You can only have 70 players on your team (or in other words provide 70 total scholarships). Even though you offer 25....if you have 65 returning players.......you will not be able to provide them all.
Available scholarships are the # of players short of 70 you will be after the season (when all the seniors graduate, juniors leave early).
So Example:
68 total players on team - 2 scholarships not being used
7 seniors - 7 scholarships become available when season is over
2 stud juniors that will leave (you will know when season is over) - 2 more unused scholarships
This leaves you to be able to add (2+7+2 = 11) more players (or available "unused" scholarships). Anymore and you will have to cut someone (either already on roster or one of the recruits). So the suggestion is to take the available scholarships (11 in this case) and add 3 (for extra because you wont get everyone you initially go after, you may have some recruit busts, or you can cut someone weak on your team). So you should not have more than 14 (11+3 extra) players on your board. Because going anymore and you are going after guys that you wont be able to sign. and (as recommended here also) dont go OVER 15 (even if you have 17 seniors leaving). Keep focused on those recruits.
I hope this helped. If not let me know and i can try again.