There are two marks at the top end of the temperature gauge, is the first one the 80% mark and the one above that, immediately below the "H" the max position possible?

I ask because my lower radiator hose popped off this morning on the way to work because I forgot to put the clamp back in place the other day during my pulley install attempt.

I was a short distance from work and was able to pretty much coast most of the way in.

At lunch I went out, got 2 gallons of pre-mix coolant, put the hose back on, got the clamp on and put the coolant in. Ran the car at idle for about 5 minutes, all seemed normal.

End of the day, I'm coming home and shortly after getting on the road, the temp gauge goes up to that first top mark but then comes down again. I figure maybe there's air in there.

I get down the road a bit more, temp gauge is anywhere from the middle to that first upper mark. I pull into a lot, shut down, let it cool a bit and then add the rest of the 50/50 coolant I had left with the engine running. I see it burping out the top of the radiator and figure air again. Nothing leaking out the bottom so I know that lower hose is OK.

I get on the road again and the temp gauge goes right back up, but not past that first mark. I pull into a smog check place and the guy lets me fill up one of the empty coolant gallon jugs with water. I put about a quart in the resevoir and the rest into the radiator with the car running.

I drove that last mile home and the temp guage stayed put just below the mid point. Parked it out back, let it cool, check the level, all ok, no leaks. Drove out for take out Chinese and all is OK. Got on it just a bit to see what's doin and all seems normal.

Going to drain out the water and replace with coolant this weekend.

Was it a combination of air in the system and low coolant level? Any damage done to anything from the near constant high temps? The whole time I was VERY easy on the engine, getting enough speed just so I could then cost at idle and the gauge never went all the way up to the mark immediately under the "H".