The doctor calculated your theoretical maximum heart rage (220 minus your age which is 160) then he only had you go up to 85% of that heart rate to see what your heart would do.
The MET score you got was not good or bad, because he didn't allow you to see what you could produce with a full effort.
If you had been allowed to go as long as you could, then your score would mean more. So your score of 7.7 only tells you that your heart behaves in certain way at that 85% level.
To rank you, for your age, you would have to be allowed to see what your true maximum is.
Depends on what your doctor was giving you the test for.
Did you have any problems or angina?
Or was this just a routine test?
Not a very useful test unless they had reason to be looking for something unusual based on some symptom you had mentioned.
Or it could have given to you based on something they noticed on a stationary EKG test and they just wanted to check it out.
You need to ask the doctor why he was doing the test.
The fact that it wasn't stopped prior to hitting the 85% mark is, all things being equal, a positive sign.
However it doesn't tell you where you rank with others your age.
Too often doctors conduct these tests in a one size fits all manner.
Everyone is taken to 85% of a theoretical maximum heart rate, when the reality is that many people will have a much higher maximum heart rate and thus they would NOT have been tested at a proper level of exertion.
For some people, age 62, they might need to take their heart rate beyond 136 before some unusual symptom might occur.
Too bad the doctor didn't allow you to go as far as you wanted, or until something unusual was seen on the equipment.
At the very least, you could have seen what your true maximum MET score was.
Again, I don't know why the doctor did the test so it is hard to give you a full answer as to why he ended the test at 136 (85% of your MHR)
You were hooked up to an ECG (right?). A cardiologist would normally review your treadmill stress results, and prepare a report for your family doctor. I suggest you ask for a copy of that report and seek an explanation from your doctor about any points of concern (perhaps you've already done this?). My own stress test results were described in terms of how I ranked with others of my age (my first MET was 10% below, my followup two years later and after losing 25 pounds though a bit less conditioned due to a month long heatwave, was 10% above).
If you were age 30-49, then a MET of 7.7 would be classed as below average (average for that age range being 9-12 MET). I couldn't find a table for your age range but I'm confident 7.7 is likely close to the average expected for your age (however, likely at the low end in my estimation, so perhaps room for improvement). Why not ask your doctor or the testing clinic what the average for your age range is?
If you're overweight (or more to the point, your body fat content is pretty generously outside recommended fit guidelines for older males), that may be something to work on, along with seeking out more activity (regular walking if that's safe, brisk walking's even better if that's also safe).
It depends how far the treadmill had got. If the treadmill was steep and going fast then 7.7 is pretty good. If the treadmill was going very slowly and was flat, then a MET of 7.7 is very poor. Met is simply metabolic equivalent which starts at 1 when a person is sitting at rest. Walking at 2.5 mph is around 3 mets. Sexual activity is around 6 mets. Very vigorous exercise such as pullups, situps etc are around 8. General jogging is around 7. So if the treadmill was steep you would be fine with 7.7 because the energy required is roughly the same as general jogging.