help! extra scoop of formula

freaking out here help me 😩 please don't judge me! Lol , My baby was with my SO mother today as we had to get some stuff done! On my return she explained she had to throw a bottle out and start again because she lost count of the scoops. I then explained I don't usually forget because with the aptimal it's 1 scoop per oz? She then explained she was putting in accidentally 1 extra scoop all day!! Because her other grandson is on a formula that for every 4oz of water it's five scoops! 😩 (in hindsight I should of explained to her how to prepare the bottle but I just assumed she knew and I didn't want to offend her) 

Anyway my son had 3 bottles at his stay with her since this morning which equals to 1 extra scoop per feed, I am absolutely panicking 😱 what should I do, will he be okay or should I take him to the ER?