Signal strength and signal quality are two different measures. Signal strength shows the physical strength of the RF wave. Signal quality shows the level of errors and interference. The two measures are not the same. It is possible to have a strong RF signal with poor signal quality (i.e. error filled).
Tablo shows a static, one minute appraisal; it is not an ongoing monitor. Signal strength could be up at 9:15 and down by 10:30. Five green dots does not signify an ongoing strong signal nor necessarily a quality signal.
There are better, more dynamic signal monitors that show more aspects of a signal (like the ones above and others). At best Tablo’s signal meter is an advisory one - not a definitive one.