Formatting rule doesn't work when asked to verify two values are identical

Hi there,

I have been having a problem with formatting rules recently. What I want is really straightforward, I have 3 boxes, A, B and C, and I want to make sure that A+B=C all the time.

If C-A≠B then B has to fill with red background. BUT it doesn't work, even when C-A=B box stays red

A B and C values are entered manually and aren't formulas, and are numbers with 1 decimal.

In my case:

A=1197.6

B=53.3

C=1250.9

What drives me crazy is that it works normally for other values, let's say 1.2, 1.3 and 2.5, everything works fine, but for the values above, it doesn't work.

Even worse, A and C are also ruled with the same logic:

A is red if A≠C-B, C is red if C≠A+B.

So everything should be red or white altogether, but in this case only B remains red with 53.3 value

I tried several different things:

I also tried with a simple addition, like typing "=53.2+0.1", it also doesn't work.

If I enter 53.2 in B and 1250.8 in C (removing 0.1 both sides), it works perfectly fine, but if I add 0.1 on both (53.4 and 1251) it doesn't work too

Anyone have insight of this issue?

Sorry in advance for the poor description, I don't use Excel often and only for simple stuff, and English is not my first language.

Cheers

Excel is 16.103.1 version operated on MacOS 15.6.1