Gradebook

Hi Greg,

It looks like you are using SWM and you aggregate only non-empty grades.

So, in your second example you have student who got 716 points out of possible 1050. And none of the grades (category totals in your case) that contribute to the course total were empty.
716 is 68.19 % from 1050 points, and this is what you see.

In your first example -  you do have bunch of empty grades with SWM aggregation type. And the grade is caluclated as 162 out of possible 235 points there.
Try to  manually calculate them  using this sample formula: http://docs.moodle.org/en/Category_aggregation#Simple_weighted_mean, and you will end up with that 68.94 thing.

(1x10 + 1x10 + 1x10 + 0x10 + 1x10 + 0.5x10  + 1x5 + 1x5 + 0.4x5 +1x5 +0x5 + 0.66666X150) / 235 = 0.68936...

p.s. So calculations are correct in both cases.
If you want to make the second schenario to be the same as the first one, try checking the "Aggregate including subcategories" box for the Course Total (in the Categories and Items interface).
This options needs to be enabled on your installation by the admin.