69 isn't bad. The real question is finding your maximum heart rate (MHR). The formula 220 minus age, was intended to compare populations, and ends up being valid for only about 50% of individuals. You may have a (physically) small heart, which has to beat faster to provide adequate blood flow. I have talked to runners who have a maximum around 220 and even after several minutes recovery they would be around 130. (Mine would usually be under 100 by then.) At any rate, if you can find your MHR it can give you a better idea of where 140 relates to exertion level. The answers in the link you gave were in some ways a little simplistic. On the other hand, many (most?) of us run by "feel" - how the exertion level feels. And it generally works as well as the monitor.
As far as the monitor goes...I had one I was using on a long run, kind of warm day, running at about 155 bpm. As I was going past my brother-in-law's house I stopped to talk to him. After standing in the shade for 15 minutes, the monitor still read 150. So I chucked that one.
Ways to approximate your maximum.