What you need to do is just to remove the Commitment Item from the context.
Basically if you understand the context then it would be very easy for you to understand why this issue occurs.
When you are dragging any measure after dimension that measure will be aggregated accroding to aggregate function defined at universe level.
Now let's say in your case the function defined is SUM so you measure Commitment Budget will get rolled up(summed up) according to both the objects Fund center & commitment items.
Now when drill down there is aggregated value is been showed for commitment Budget object which is added to actual value of commitment budget measure.
Because of this reason you are getting double amount.
You can go for any formula mentioned below
1) =sum([Commitment Budget]) in ([Fund Center]).
or
2) = sum([Commitment Budget]) forAll ([Commitment Item]).
I think rather then jumping directly to solution first understad the problem and then solve it.
Does it make sense!!
Please let me know
Thanks,
Swapnil