For sure, it would certainly be clearer to say “the large charged lemonade has about the same amount of caffeine as four cups of coffee.”
I also just saw that a cup of coffee is less than 1 cup, so maybe it’s actually closer to five cups of coffee. Either way, I agree they could have made the comparison more explicit.
Talking about heavily-caffeinated beverages reminds me of the time I tried to order a venti nitro cold brew at Starbucks, and the guy actually told me “I’m not supposed to sell you the nitro in venti, actually…” But I must have looked like I needed it, because he looked around to make sure his manager wasn’t watching, poured me a venti, and rang it up as a grande!