If you download exactly the same data it will be exactly the same size.
However some websites have separate 'mobile' versions (which have been deliberately optimised for use on smartphones or tablets) and many now use 'responsive' designs, where there's only one website but the data it actually supplies to browsers depends upon the device which it's to be viewed on. (The Answerbank is a responsive website).
So it's possible (but by no means certain) that viewing a website on your phone might use slightly less data than when viewing it on your computer. However the faster loading of pages on your phone is more likely down to the different ways that the Windows and Android operating systems work (and/or to do with differences in the browsers which you're using).