As user poachie mentioned above, those settings have zero effect, at
least in the sandbox account I'm using, when processing transactions
with Accept Hosted.
I just ran into this myself, still not fixed after 2+ years. I mean, we
can just take the resize values sent from Authorize.Net and add some
hardcoded number of pixels to account for the size of the captcha
button, but it's kind of annoying that the ...