The fixed overlay bar in the bottom of the IMO boxes are the new tyre indicator,
it is shown until you have scrubbed in the new tyres and maximal grip is achieved.
If wear mask is not used, you can also see the wear bar starts a bit from top, to after a few laps/corner rise to top level.
the 0-100% bar above in the same IMO box, are the ring temperature overlay, see post #62 above for more info
all features can be switched of if you like by editing the ini file
[INDICATOR]
show_new_tyre
False -> no indication of new tyre
True -> indicate new tyre status, resets at wear level 100%
temp_bar_mode
None -> no temp range bar
StandardRing -> average ring temp as range bar overlay in IMO box
[WEAR]
masked
False -> new tyres will show some wear before it goes to no wear, depending on tyre it takes a few corners to a few laps (AC default behavior)
True -> new tyres show no wear from start