I attached the conditional formatting for a calculation field that displays as a percentage. Based on the value it should be filled with yellow but it shows as red (see 2nd attachment.) I tried using decimals and percentages in the conditional formatting but that didn't work either. What am I doing wrong?

Since it is a percentage you should use decimals in your calculation formula:

Value is between .9 and 1

Value is between .79 and .9

Value is < .8

Also there is some overlap in your values.