I remember that it was determined by the available hard drive space you have.
You do have a second drive (your audio drive) that you record on to right? If not, I'm going to warn you of a big issue: Recording with logic into your internal system drive CAN result in a corrupted system, and the only recovery is to wipe the drive, and start again. Personally had this happen (after doing this exact this for quite a while). The Apple tech was very clear: DO NOT DO THIS!.
Anyways, try a bigger drive to record on... does it get larger that way?
The other thing you can do is increase the song length: in the transept, below the time signature field, there is a number, (defaulted at 130 bars I believe). Increase that number and see if that helps...
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