I am trying to find the line of best fit and this makes no sense at all.

I have a table - here are the values for x, length, and corresponding values for weight, y

60 1-5
62 114
64 124
66 131
68 139
70 149
72 158

I'm asked to find the line of best fit and round to hundredths.
When I do that, I come up with: y = 4.36x - 256. 14

Then, the question asks how much I would expect something that is 75 in length to weigh.

So, I do: y = 4.36(75) - 256.14 and get 70.86
This makes absolutely no sense based on the table!

Where have I made my mistake?
Thank you.