sudo fsck.vfat -v /dev/sdb1
fsck.fat 4.1 (2017-01-24)
Checking we can access the last sector of the filesystem
0x25: Dirty bit is set. Fs was not properly unmounted and some data may be corrupt.
1) Remove dirty bit
2) No action
? 1
Boot sector contents:
System ID "MSDOS5.0"
Media byte 0xf8 (hard disk)
       512 bytes per logical sector
     32768 bytes per cluster
         6 reserved sectors
First FAT starts at byte 3072 (sector 6)
         2 FATs, 16 bit entries
    123392 bytes per FAT (= 241 sectors)
Root directory starts at byte 249856 (sector 488)
       512 root directory entries
Data area starts at byte 266240 (sector 520)
     61591 data clusters (2018213888 bytes)
63 sectors/track, 255 heads
        32 hidden sectors
   3942368 sectors total
Checking for unused clusters.
Perform changes ? (y/n) y
/dev/sdb1: 144 files, 39219/61591 clusters