If there's no clear, most floor epoxies will take another coat of the identical epoxy after a few months.

With clear lightly scuff (goal is to dull the sheen, not necessarily to remove the epoxy).

Clean very well, then apply a second coat on a nice day. Low humidity and not super cold weather (see your kit for specific temp recommendations). Low-mid humidity is just as important though.

That's the negative of applying the clear.

Without the clear it's simple, buy another kit and touch up the damaged area once clean. The clear coat makes issues like this difficult.

Not 100% sure on the fix when clear is involved, call the hotline & they'll give you the proper answer, but they'll give you a literal by the book answer. Floors are costing to repair issues thus the defensive instructions.

Try to get them to give you an idea that isn't by the book & you fully understand they won't be held accountable if it fails. Floor coating companies by the book won't recommend something even if 90% of the time it will work.

Perhaps a light sanding of the areas will suffice, recoat those areas with the kit and then reapply the clear. Run that by them.

The tempature has a lot to do with this.

Since the clear coat depends on your needs really, preferably you'd wait until spring/summer.

Think surface temp by the way, not air temp. If you heat up the garage real quick to 65 the concrete itself is still likely very cold so you'd want to prep the temperature ahead of time to warm is as well.