What does memory unit # blocks mean for xbox?

[Macahan]

Before I started playing JA on xbox I deleted all

games from my hard-drive so I would have plenty of

memory for saves. Every 5 minutes or so I would

save and then delete the previous save. When I

got close to the end of the game,just before the

second battle with Alora, I tried to save and got

a message that said "not enough memory on the

hard-drive"! I looked at the back of the game

case where it tells you what features the game

has,the feature it did not have was memory unit

# blocks. Does this mean the game was designed

only for so many saves?