Regarding the 4 in the UUIDs this stands just for version 4

c56f1a0e-4ef6-11e8-9c2d-fa7ae01bbebc

xxxxxxxx-xxxx-Mxxx-Nxxx-xxxxxxxxxxxx

The four bits of digit M indicate the UUID version, and the one to three most significant bits of digit N indicate the UUID variant. In the example, M is 1 and N is a (10xx), meaning that the UUID is a variant 1, version 1 UUID; that is, a time-based DCE/RFC 4122 UUID.

from:

https:// en.wikipedia.org/wiki/Universally_unique_identifier#Format

try it:

https:// www.uuidgenerator.net/