This is the LTD/R indicator (LASER TARGET DESIGNATOR / RANGER) on the ATLFIR
Laser Status Indication - The laser status display provides 6 labels as follows:
LTD/R is not flashing in Go Fast, note the ATLFIR sim manual here only mentions use of the LTD/R in A/G (Air to Ground mode) The ATFLIR here appears to be in A/A mode by the configured display options.
- LTD/R (flashing) - Laser is firing with ranging available.
- LTD (flashing) - Laser is firing with no ranging available.
- LTD (steady) - Laser is in standby.
The manual also says LTD/R then switches to LTD only in the display statuses, this could be a typo in the manual, or some version difference between the sim and the real ATLFIR. Or it could mean that the display shows it as there in A/A mode but there is no option to use it in A/A mode.
The following video contains a montage of ATFLIR footage showing LTD/R flashing but also positioned immediately underneath the pointing direction indicator. I thought it might be possible he's just referring to the indicator being in that general area, which depending on the model of ATFLIR he is probably right according to the footage.
Buuut he also seems to be doubling down on the pointing direction indicator also being the laser fire indicator.