calories counters on equipment at gym?

jdm1954

I have seen statements that the calories counter on treadmills etc are not too accurate and will give a higher than actual calories used count. When I start on the treadmill or whatever at the gym, I will punch in my age & weight (about 214) Do you think I would get a more accurate count punching in my age and lower weight? I try not to do the same routines too often so my speeds and inclines will vary so it would be hard to calculate on paper I think.
Or has anyone heard what the typical manufacturers overstatement of calories is?