Circular radial gradient

Question

„Add a circular radial gradient to produce red and blue, with color stops accordingly at 15px and 25px“

I‘m not sure because i‘m a nooby, but is the description maybe wrong?
Or did i just don‘t understand why the color stops at 25px should be written 50px in the answer?
It also could be that i have to fill in the half of 50 which is 25, of course.
Than i just haven’t figured out why, but than i‘m sure i will learn it soon ;-)

Answer 1

background: radial-gradient(circle at 50%, #f00 15px, #00f 25px);

Answer 2

ty ;-)