Yes Magdalena, this would be the correct interpretation for the data. 
Although we usually expect more lesion to be associated with worse performance, it is possible to find the opposite effects. 
Imagine comparing participants with ACA and MCA strokes. Also imagine that your primary DV is speech fluency. 
Having a larger lesion to the ACA might predict higher language fluency scores, because having a lesion to brain areas supplied by the ACA means you likely DON'T have a lesion  to brain areas supplied to the MCA (which matter more in terms of language function).
Hope that makes sense.
Best,
Roger