Annular Width is the distance between the side of a pad, and the side of a drilled hole. It basically sets the tolerance for mis-alignment between pads and drilled holes.
In the board setup, this is an absolute minimum value (in your case 0.1mm) and it should set to the capabilities of your board manufacturer (0.1mm is already quite small. I’d rather set it to 0.2mm or so, but you should really look this up in your PCB manufacturer’s capabilities).
Yes, (too) small annular width is a pretty serious issue. You should not ignore it.
So why does pad 1 of D4 only have an annular width of 0.085mm?
I don’t know.
I just selected the symbol LED_RKGB,
added the footprint LED_THT:LED_D5.0mm-4_RGB
and then updated the PCB Editor.
That’s why I’m wondering why an unchanged footprint from /app/extensions/Library/footprints/LED_THT.pretty doesn’t meet the requirements.
Looking at the V9.0.1 library and the Kingbright datasheet.
0.9mm hole is correct.
The pads are 1.07 wide, so the annular is 0.085mm - very thin
Pad to pad gap is 0.2mm
The Kingbright datasheet has warnings about stopping the leads shorting. They are really close together.
If you can, use one of the alternate footprints, either the staggered leads or the spaced leads. Either of these keep the pads much further apart and reduce the shorting risks. The benefit is easier PCB manufacture. The negative is having to form the LED leads and a little more PCB space used.