Math Help - A little confused.

It is asking me to construct a Histogram and I have use the frequency distribution. I know the rule, is that the maximum data value - the minimum data value and divide that with the classes. And whatever answer you get from that(round up) and you add to each. So, I was originally making my table ass 400,450,500,550....850 and inputting the FICO scores. What I am trying to ask how did the scores jump up from 400 to 424.5? I did the frequency distribution method and it did not pan out for me. Can I get some help? TY

I am putting the picture up but it does not seem to come out.

NM I figured it out.