A single request for first aid causes two runs of fsck_hfs(8), both of which have file system check exit code 0, zero (the volume appears to be OK). More specifically: the first run of fsck_hfs is preceded by, and followed by, Core Storage stuff – a reported fix (growth) of the LV, to fill the LVG – then a reported growth of the file system and so, there's the second run of fsck_hfs. A second single request causes another two runs, and the reported size of the grown LV is no different from the size that was reportedly a fix in response to the first request. To other users of Core Storage: is the 'one request, two runs' symptom familiar? I probably reported some 'multiple run'-related bugs years ago, I suspect that this is an old fsck_cs(8) bug that will not be fixed.