Hi Rapid. I researched on line , recovery heart rate and found the important number was how fast your heart recovered after stopping for one minute.
There is a formula to work out how fast your heart should go when you exercise, i.e you calculate your maximum heart rate for your age and then exercise at 85 % of that number.
That is a bit difficult to measure while actually on an exercise bike working hard, so I just rely on going as fast as I can , just into the realm of discomfort , then after stopping I measure my pulse at my throat for ten seconds, wait one minute and take it again. Multiply your number by 6 to get the pulse rate for a minute. The drop after one minute should be 30 plus, or up to 59 if youare super fit.
e.g .I started doing HIT for 20 seconds but do HIT now for one minute, get my pulse up to 24 per 10 seconds, then after one minute it’s 18, so has dropped 6 , or 36 per minute. From 144 to 108.
If after one minute your pulse is still going fast and has only dropped 20 or less you are in poor shape and perhaps need to get medical advice before doing HIT. But in your case it sounds like your recovery is fast and you are fit.