B78AFDECC (hex) = 49,269,432,012 (dec)
This is probably the number of sectors. WD should use 512 Byte units for each sector; although today's disks use 4K internally, this particular HDD is a 512e HDD.
If we multiply the number above with 512 we get 25,225,949,190,144 Bytes, which is roughly...