Mature Metal discussion

Team, I’m looking for some guidance! I’m a bit puzzled about how to measure the length. My CB3000K device is in play here. When I take measurements while wearing it and I’m flaccid, I subtract half an inch from the tip measurement, which gives me 2.5 inches. However, if I measure without the device directly from the base of my penis to the tip while flaccid, it also reads as 2.5 inches. Should I still go ahead and deduct that recommended quarter-inch mentioned by MM? Thanks a lot for your advice! Really appreciate it!