Hi, I did not check the details but
looks weird to me. I'd write A=(0.2600 ± 0.0005) m, etc.
In the table
I'd write 2.84 ± 0.04, etc.
Also in table 3 I get suspicious because the lesser is the calculated c value, the lesser the error you get. Using my intuition the opposite should happen.
Maybe I was not taught the right way though and keep in mind that I'm just an undergraduate student.