Cobra 2000 GTL PLL MB8734 off frequency

Hello, I am working on a Cobra 2000 GTL. I am starting to align it or check that it is aligned. The first step is to check (TP13) pin 8 on MB8734. The service manual says to check for 10.240 MHz. I get a reading of 10.238 MHz . Is this ok or does it need to be exact ? What would cause this ? Two of my frequency counters get the same reading of 10.238 MHz. Do 10.240 MHz crystals go bad ? The service manual says there is no adjustment for that step.