mkisofs: 2.01a03 ChangeLog explanation

[Eduardo Pérez <eperez@it.uc3m.es>]

I was reading mkisofs ChangeLog at 2.01a03 and found this:
-       The final padding that is added by default is now 150 sectors
        which is the required size of the track post gap on a CD.

Could anyone point me what is this?

It seems that is on the standard.

What was the previous behavior?
What OSs, CD-Readers and embedded devices require in this matter?

Merry Christmas,

Eduardo Pérez