Stu wrote:
I have a cell formatted to show a number as percentage and the conditional
formatting rule says Between 0.9 and 1 will be green. 0.9 is showing up no
color
but any value from .91 - 1 shows up green. Should "between" .9 and 1 include
.9?
Is this a known bug?

No, "between" doesn't include either of the two ends. If you want to include
0.9 and 1.0, do something like this:

Formula is:

=AND(A1=0.9,A1<=1)