Runways aren’t important, planes are. Using missiles to destroy concrete is not cost effective. Assad just lost 20% of his Air Force. He can’t sustain another loss like that.
But did he lose that rag-tag but efficient AF pilot and commander that we know of in the mix, and his proteges.
There are plenty more airplanes in Russia. Depending on how Putin wants to play it, he can sustain losses like that for a long, long time.
“...Up to 20” can mean 6...The number will not exceed 20.