Ender 3 measurement of extruder filament

I am quite new to 3D printing and was trying to check the extruder setting on my Ender 3 but I must be doing something incorrectly!
I go to prepare on the screen, then Move Axis, then extruder and Move which i click on 10mm then set extrude to 100mm but the machine only extrudes 40mm. I have repeated the procedure a number of times and it still does the same thing! The step[s set in the menu is 93. Any suggestions as to what may be wrong.

Update: Since posting I have done the calculations as per suggestion and as the E setting was 93 and I was receiving 40, 93X100/40 came out as 232, so I reset the E steps to that figure and now get 100 mm when asked to extrude 100 mm, with 100% repeatability!! Do not know why but seems to have fixed it !!!???
Thanks in advance