Don't listen to cat, verify what pan your engine has yourself by looking at page 2 here.
The shallow pan is sheet metal steel, and the deep is cast aluminum fwiw.
The capacities in the chart is total oil makeup volume. So, if you have the shallow pan, it takes 19 quarts after an oil/filter change, and that includes volume in the filter. So long as you don't have any extra filters, centrifuges, or coolers in the system.
Your steps to recalbirate the dipstick are close. Here's what the service manual says. To remark/calibrate your dipstick, you can use a scribe, but I prefer a sharp flat cold chisel.
If you've got the 19 quart capacity/shallow pain. Drain oil and replace the filter. Add 17 quarts, start the engine and let it idle for 2 minutes. Shut it off and wait 10. After the wait, remove dipstick and mark where oil level is. Reinsert the dipstick, then add remaining 2 quarts and wait another 10 minutes. Scribe line at new level and you now have your add and full lines.
The c7 had an original design oil capacity of 5 and 7 gallons, but cat quickly found it was too high and created excessive crankcase turbulence. Lowering capacity a quart or two solved the issue.