This is what happens when chemistry nerds try to be comedians! Rating something "14 on the pH scale" is chemically impossible since pH only goes from 0-14, and calling it "very basic" is a perfect double entendre. In chemistry, bases are substances with pH values above 7 (like bleach or ammonia), while in slang, "basic" means unoriginal or mainstream. So this meme is simultaneously saying the joke is extremely alkaline AND painfully obvious. The unimpressed expression really sells the whole "I'm judging your humor with science" vibe.