Oh, yeah..... stoopid me was trying to read the numbers. I didn't bother looking at the intervals along the top.
On a 30" do they go 10 - 20 - 30 ?? If so, just squish them in like he said and open up to a complete 28.2". Yours looks like 27.79. You'll hafta play with your pinch rollers a little more to get it to fit as is.
Ours is a 54" and we usually have them set to around 52.8". Can go pretty far like that.