tig glass cups with no numbers and flow rate?

I noticed that glass cups do not have numbers on them. What is the rule used to set the gas flow rate with such cups considering that we will be using screens?

measure the cup, each number corresponds to 1/16th of an inch. Rule for gas flow as per Weld Coach https://youtu.be/RKqTLRw-NxY?t=269

cup size x 2 = min gas flow in cubic feet per hour and x 2.5 for maximum flow

cup size = min gas flow in liters per min