I still struggle a bit with radial-gradient syntax, but you have the right idea, except 80px doesn’t necessarily mean that’s the size of the gradient. The radial gradient size is in the beginning of the syntax, and here’s where I get confused, because the -moz- gradient syntax is different than -webkit-..
Both can handle keyword sizes like `circle closest-side` or `ellipse farthest-corner`, but when talking about pixel based sizes, it gets murky.
the first two values are position: 0% left, 100% from the top (so the bottom), the size of the gradient is 3.5em width, 8.25em height. The design of the gradient comes out as a vertical ellipse, and 30% of the way through, it stops being transparent, abruptly goes to a dark gray, then transitions to a white.