Printing faster than volumetric flow rate should allow?

I’ve been trying to shave some time off a big print I am printing lots of copies of. I did a lot of tweaking, and used a volumetric flow rate test print (I’m not at home so I don’t have a link handy, it was on printables I believe) with some Creality PETG I just got. Based on the test, 23mm³/s was the max, but layer adhesion was weak, so I set it to 17.

I’m using a .4mm nozzle.

So, with a line width of .42 and a layer height of .25, 17 / .42 / .25 = a max speed of 162mm/s. Is that math correct? I believe it is.

The issue is that when I slice the model, there’s a lot of it (the inner walls) that are supposedly printing at 230mm/s, the max speed in this profile for inner walls.

That SHOULD be impossible. Unless I’m fundamentally misunderstanding the math, but I googled the formulas a few times to make sure.

What am I missing?

Thanks for those ideas. I’ll check them next time I’m near the printer.