basics of transformer

I have a 40VCT .25A transformer and I'm wondering what those numbers mean..

does the 40VCT mean 40VAC from the center tap? If so across its full
secondary its 80VAC? and the .25A means that it can handle at most .25A
across its secondary coil(since its a step down from 120VAC the max current
in its primary should be smaller... ~80/120*.25?).

Also should I assume these are all RMS values? When I put my variac up to
100VAC and hook it up to my transformer I get about 40 volts across the hole
secondary(hence 20V's across from the center tap). But this means that at
the mains(117VAC?) I'll be getting more than 40VAC across the full
secondary? Is this ok to have the transformer have a little more than its
voltage rating?

Thanks,
Jon


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