The Resulting Slice

This thorn normalizes things so that if there is no perturbation, it produces a Schwarzschild ($=$ Brill-Lindquist) slice of the $m=2$ Schwarzschild spacetime.^part331 You can't change this mass. :(

In any case (perturbation or not), this thorn also reports an ADM mass for the slice. This seems to be pretty reliable.