Dear Feng,
The correction is more complex, resulting in the discrepancy you observed. FWE-R p values are corrected with regard to Euler characteristics, not just the resel count (see e.g. http://www.fil.ion.ucl.ac.uk/spm/doc/books/hbf2/pdfs/Ch14.pdf or http://imaging.mrc-cbu.cam.ac.uk/imaging/PrinciplesRandomFields ). This is especially relevant for small volume corrections, in which the shape of the search volume has a larger impact.
Best
Helmut
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