why can I say that
$ \int_0^a t^2 dF(t) = \int_0^a t^2 d(F(t) -1) $
unfortunately my experience with the Riemann -Stieltjes is practically non existent, so for instance I do not understand, why the interval of integration is not affected by the change of the integrator.
Appart from the lack of understanding mentioned above, my second question is, whether I can basically make sense of the change of the integrator in the same way I do in the Riemann context for a change of variable via the chain rule ?