190*F would be about 0.64 volts at the ECT.
210 would be just under 0.50 V.
I'd check with your DMM to see if you can interpolate which reading is more accurate.
FWIW, I've checked gauge calibration on my ECT vs the AM gauge (the AM sender is located in the stock sending unit location). Though the sender and sensor (gauge and ECT, respectively) are in differing locales, they were within 1* of eachother most of the time. At about 185*F I noted a 4* lag in the ECT. This lasted for about 15 seconds and then caught up. I know that doesnt help you, but maybe it gives an example of how my car is.