Also, note if you have an intro, say 8 bars, then you would have the first box say 9. This can be very useful if the first part of the song is not just a simple intro but a completely different part from the rest. You could have the chorus start at bar 51 if you wanted to and use the first 50 bars as an extended section as opposed to just an intro. The chorus starting at bar 51 could be say 40 bars long so box 1 would be 51, box 2 would be 40, have the choruses repeat as many times as you wanted as indicated in box 3. Then you still have 1st, 2nd endings within the choruses and a tag or coda for the end. Biab is very flexible once you learn it. This means you could create an opus with a long first section with an intro as part of it, multiple repeats in the middle using choruses and 1st/2nd endings and a third section could be an extended 30-40 bar tag or coda going to a final ending. With all of this plus some creative thinking on your part you can create pretty much any song form you need in Biab.
This is an extreme example, some people working with something that complex would not use any choruses or repeats, just do the whole thing as one long aong. This is referred to as "unfolding" the song. The only thing is there's a hard coded 255 bar limit. If you really need more bars than that, then you move it into Real Band.

Bob

Biab/RB latest build, Win 11 Pro, Ryzen 5 5600 G, 512 Gig SSD, 16 Gigs Ram, Steinberg UR22 MkII, Roland Sonic Cell, Kurzweil PC3, Hammond SK1, Korg PA3XPro, Garritan JABB, Hypercanvas, Sampletank 3, more.