This was my logic too, but I think the expected value of each girl is actually 3.5. Possible value are 1, 2, 3, 4, 5,6, so the middle is actually 3.5. So 5 is your save bet (3.5 * 5 = 1.7). 4 and 6 would put you just over and just under (expected).
Edit: Which may explain how you ended up over, but there is randomness so it’s not a perfect science.
This was my logic too, but I think the expected value of each girl is actually 3.5. Possible value are 1, 2, 3, 4, 5,6, so the middle is actually 3.5. So 5 is your save bet (3.5 * 5 = 1.7). 4 and 6 would put you just over and just under (expected).
Edit: Which may explain how you ended up over, but there is randomness so it’s not a perfect science.