It would be nice if you provided copy-pasteable code rather than a screenshot, but...
The error is telling you that the step (in this case assumed to be 1) is not compatible with the range bounds. You can reproduce this simply with
NSum[x, {x, 0, 11.3}]
I don't know the rationale behind this (Sum seems to work differently), but it clearly expects that the range is perfectly divisible by the step. So, this actually works:
NSum[x, {x, 0, 11.3, .1}]
