HOW IS BLOCK TIME USED WHEN RECORDING?

In most cases; my studio included, the "block time" price you're getting is for that day only. Studios like to give a better rate for this because it usually means you're renting out the studio for several hours if not the whole day. Studios have to prep and de-prep a session so it works out better for the studio and the client to just book in half-day or full day increments because it's not very advantageous for a studio to set up a whole session for just a 1-2 hour session. For 6 hours I would be willing to split that into 2 sessions, but usually my minimum and most professional studio minimums are 4 hours, the exception being for commercial voice-over productions. It never hurts to ask though.