Total noob question about my full service bank (I didn't see anything in the Sked Ref Guide about this, please let me know if I missed it).

This is my first time using my bank. In Mar I've done one 1-day GS (worth about 11 hours).

On the bank page it shows "avail deposit credit" of 7:32. Before the GS I was just over the ALV. My question is, why can't I put the full value of my GS in my bank?

And then when I decide to use my hours from the bank later on how many can I use? It says to fill up, so can I only use it if I'm below ALV to get up to ALV?

Thanks guys.