If all those births are the same couple, it constrains Miss Maxwell's date of birth.
She could not have got married until she was at least 12, so she could not have been born later than 1729.
And her youngest child was born in 1775 so she cannot have been born before 1725.
A marriage at 12, although legal, was very rare, and births to mothers over 45 were also very unusual. So I think these have to be at least two different couples.