Measuring cups

 We were learning about Measuring our cups and our dads favorite cup,so i was measuring my cup and see how many ml it can hold and i guessed how many and I said maybe 500ml but when I put the water in my measuring cup it was only 300ml after that I did my dads mug and I guessed between 400 and 500 but it was a bit between 500 and 600 mil.