How to measure RFID latency (ms) to respond back to arduino or computer.

Hey guys! I'm quite new to this forum, and I have a project that includes the use of an Arduino Uno R3, and the use of an RFID scanner to scan and unlock a solenoid lock. I initially got the source code from a youtuber, and added the libraries needed for the rfid scanner. So far, it works and opens the lock when put to the right card, and rejects it when not. However, I want to try something new. I'm trying to measure the time it takes the RFID scanner to respond back to the arduino. Is there a way to do this accurately through code? Any help is much appreciated! Thanks again!!

P.S ive tried experimenting with milis code but I have no idea on how it works.

To be more specific, I want to know how long it takes for the RFID scanner to read the rfid tag.