It could be different. One is supposed to define symbols before one starts with a Let statement, as in

Question

Let B= a constant
Let b= some other constant or
let b=B

I suspect it is a sloppy typographical error, so B+b= 2B or =2b

in math is there a differenc in B and b
for example if you have b+B
would this = 2 b? or would have to leave it as B+b