In HM, you have leveled spells (1st level, 8th, etc) and you have Apprentice (elementary learning spells) and Journeyman (secondary grade spells). Apprentice spells cost 30 Sp, Journeyman cost 40, and leveled costs 40+(10x spell level), so 50 for 1st, 60 for 2nd, 70 for 3rd, etc.. The mage can memorize 1 spell from each level, plus 1 Apprentice and 1 Journeyman.
At 3rd level, you have 260 Spell Points. 70+60+50+40+30=250. You have enough points to cast all of your memorized spells, plus 10 points over to boost some. Alternatively, you could be in a situation where you never had to cast them all. You could, in fact, cast your memorized apprentice spell 8 times, or your memorized 1st level spell 5 times, or your 3rd level spell 3 times. Any non-memorized spell, if you have the spellbook, costs double.