Explanation
Conditional formatting is evaluated for each cell in the range, relative to the upper left cell in the selection. In this case, the formula uses the MOD function to check the remainder of dividing the value in each cell, with the value in cell E2, which is 9. When the remainder is zero, we know that the value is an even multiple of the number 9, so the formula checks the result of MOD against zero.
When MOD returns zero, the expression returns TRUE and the conditional formatting applies. When MOD returns any other result, the expression returns FALSE conditional formatting is not applied.
Note E2 is input as an absolute address ($E$2) to prevent the reference from changing as the conditional formatting rule is evaluated across the selection B4:G11.
Explanation
The formula first uses the ISNUMBER function to test if the value is a number, and applies a simple logical if so:
=IF(ISNUMBER(B4)
For any number less than the value in “input”, the formula will return TRUE and the conditional formatting will be applied.
However, if the value is not a number, the formula then checks if the first character is a less than symbol (<) using the LEFT function:
IF(LEFT(B4)="<"
If so, the MID function is used to extract everything after the symbol:
MID(B4,2,LEN(B4)
Technically, the LEN function returns a number 1 greater than we need, since it includes the “<” symbol as well. If this bothers you, feel free to subtract 1.
The result of MID is always text so the formula adds zero to force a Excel to convert the text to a number. This number is then compared to the value from “input”.
