find can not find size between A and B

Question

problem description

I was using find(GNU version) to find files with size between 4G - 5G with below command

# find . -size +4G -size -5G -exec ls -1hSs {} +

But below can work

# find . -size +4G -size -6G -exec ls -1hSs {} +
4.9G ./ff84e49c231a00b2d7ed40e0ecf81cad220795bd
4.5G ./ff623cd1cdad094be418aec445e5317156e945fe

I read the man page of find get below:

         `G'    for Gibibytes (GiB, units of 1024 * 1024 * 1024 = 1073741824 bytes)
      The  size  does  not count indirect blocks, but it does count blocks in sparse files that are not actually allocated.  Bear in mind that the `%k' and `%b'
      format specifiers of -printf handle sparse files differently.  The `b' suffix always denotes 512-byte blocks and never 1024-byte blocks, which is  differ‐
      ent to the behaviour of -ls.

And man page of ls get below but still got confused:

          -h, --human-readable
          with -l and/or -s, print human readable sizes (e.g., 1K 234M 2G)       
          The SIZE argument is an integer and optional unit (example: 10K is 10*1024).  Units are K,M,G,T,P,E,Z,Y (powers of 1024) or KB,MB,... (powers of 1000).