This may clear up things.
Division I
According to the NCAA 2010-2011 Division I Manual, the first official preseason practice may not take place before the date that allows the maximum of 40 units before the first scheduled intercollegiate game. Schools calculate the 40 units by counting backward from the first scheduled game, with each day representing one or two units as outlined in the NCAA manual. Schools may not have more than 29 on-field practice sessions during preseason. The NCAA limits colleges in the Bowl Subdivision to 105 student-athletes who may practice before the first day of classes or first game, and colleges in the Championship Subdivision to 90 student-athletes. All schools must respect a five-day acclimatization period at the start of the preseason. During this time, athletes may engage in no more than one conditioning, speed, strength or agility test or one on-field practice per day of no more than three hours and one walk-through without gear. There must be a three hour recovery period between practice and a walk-through. During the first two days, only helmets may be worn. On days three and four, helmets and shoulder pads are allowed. From day five onward, full pads are allowed. Multiple practice sessions per day may not occur on consecutive days, and student-athletes must be allowed at least three hours of recovery between sessions. On single-session days, no more than three hours-on field is allowed, and on multiple-session days, no more than five hours on-field is allowed.
Division II
According to the NCAA Division II Manual, the first practice date for the Championship Segment may not occur more than 21 days before the first allowed intercollegiate game or seven days before the first day of classes, whichever is earlier. Division II requires a five-day acclimatization period with the same restrictions as Division I. Multiple practices may not be scheduled on consecutive days. On both single-session and multi-session practice days, Division II limits on-field time to three hours. Weight-lifting is not considered on-field time. Division II may hold up to 15 spring practice sessions. The Non-Championship Segment of Division II may not practice before February 15 and must finish practice at least seven days before the first date of final exams.
