Most of us don't even bother with pH.

Mix the stock solution per instructions using a reasonably accurate measuring device. Mix the working solution using a reasonably accurate measuring device.

I don't use Ilfosol but when I dilute my stock solution, I just use a kitchen measuring cup. It may not be all that accurate but it really doesn't need to be. What's important is you do it the same way every time. I would imagine my measurements are off as much as 5 to 10%.

Difference in dilution will affect your development time slightly which will affect contrast and density. Would you know say your film is a tad too dark or too light and just a tad too contrasty or not enough? Side by side comparison may tell it if you do that but in normal shooting, shooting variation is far greater than that.

I'd say don't worry about it and just do it. You'd be pleasantly surprised how easy it is to get a reasonably good result - provided there were no major screw ups, like using fixer first and developer second.