uh, perl gives exactly the same answer as Numbers

> perl -E 'say .1 + .2 - .3'

5.55111512312578e-17

And python actually gives one more digit than Numbers

> python -c 'print(repr(.1 +.2 -.3))'

5.551115123125783e-17

So, I'm not sure why you are claiming "there are way too many digits" and that Numbers is doing something wrong.