Telling someone who doesn't know what widening a variable means that they meant widening a variable without explaining what widening a variable means helps no one.
(Plus adding 1 bit to the "bit size" of a variable _does_ double the base 10 size of the variable if you want to be really pedantic)
This is consistent with other uses: The size of an array, the size of a data structure in general, the size of a file... In all of those you are concerned about how much memory or disk space is taken.
So I think calling the range "size" is counterintuitive and gives the wrong idea, and I do not agree that the "base 10 size" of a variable is equivalent to its range. (What does "base 10" have to do with it anyway? The range is doubled no matter what base we're operating in.)
[1] Actually multiple of sizeof(char), where sizeof(char) is defined as 1. And that's technically not 1 byte everywhere, but most of the time nowadays it is.