IGT is far less accurate than real-time. There is a Video comparing A train agent 104 to a 103. although the 104 should be a second slower, it actually finished a second faster. What makes it deviate is levels of lag, and because it is completely uncontrollable in some cases, Real-time is unreliable.

assuming you are talking about console, the only way to display the IGT to the decimal is by using add external tool, which is banned.

Speedrun.com is for emulator times. The timespage for console runs is https://www.the-elite.net/

yea the game caps at 60 no matter what