Are You Recording Your Thought Process?

An 1870 estate settlement lists your male ancestor as an heir of their grandfather. The estate settlement enver indicates your male ancestor is a minor, so you (reasonably) conclude they are "of age." Based upon this you conclude that your ancestor was born by about  1849. Did you list the estate settlement as the "source" of the approximate year of birth? Did you include in the notes HOW you reached this conclusion. The estate settlement doesn't provide direct evidence of age and the indirect nature of it (which includes your reasoning) should be discussed in your notes on the specific ancestor.