Throwing this out for whatever it might be worth (mostly because it's been a very long time since I had characters with crafting levels that low and didn't catchit), but the tooltip description for Potency Improvement 3 in the skill screen says that Rank 3 allows making glyphs of Level 20-35, but the Potency Runes for Levels 30 and 35 require Potency Improvement 4. Potency Improvement 4, OTOH, says that it allows making glyphs of Level 30-45, so there seems to be a couple of levels of overlap between those two and only one can be correct.
I'm fresh out of outrage, but I could muster up some amused annoyance if required.