compensation?

hello, i have a quick question about rates. so i recently made a poster for a family member and they asked me how much id like to be compensated. now im a beginner graphic designer, like fresh out of college, i've never charged for my work and to be honest this took me like two days total to make 10 variations. it's a really simple poster and i dont have to print it, but i dont want to under or over charge for my time, so does anyone have any suggestions on what i should say? should i charge a flat rate or should i do min wage x the amount of time it took to make? any thoughts would be greatly appreciated. thx ☺️