I have a CTX 3030...I do read the numbers...that said, I do dig all the low tones...I do tend to go past the 12-35's up to the 12-38's b/c they are usually zincs. I recognize I may be missing a big 10k class ring or band. It's a risk I assume. That said, if I am in a good zone with greenies and sinkers, I dig it all. When it's sanded in and zincs are popping up all over, I do go by. Personal choice. No more no less.
I view target selections as a function of time vs. probability of a "keeper".
The only way to really know is dig them all. I just don't have enough time or energy to hunt as much as I'd like so I play the odds.