How to interprete the output of --export-ownertrust?

[Christine Kremsmayr]

Hi everyone,

with the command gpg2 --export-ownertrust I can cause GnuPG to display 
the owner trust values of the public keys in my keyring.
The problem: I don't know how to interprete the numbers to the right of 
the fingerprints:

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C:\Users\ckr>gpg2 --export-ownertrust
gpg: verwende Vertrauensmodell PGP
# Liste der zugewiesenen Trustwerte, erzeugt am 02/28/16 13:42:21
Mitteleuropõische Zeit
# ("gpg --import-ownertrust" um sie zu restaurieren)
356EE781EE3C34C00D605BD075B39FCADA0D42EF:3:
87441C8D5FA9D2D46F3CFE8FBD17F2430CE312D4:6:
B59D9B8DA5895CF837844F4EC440EB6B86F0B249:6:
C4C3767EFE9BF995431824EF6AD043812A4BF322:6:
3C41B1B124266AF139B902F24DC129B8831622ED:5:
-----

What is the meaniong of 3? And of 6? Does anybody know what the possible 
values are that can be displayed?

Is there a mapping between these numbers and the owner trust values like 
"unknown", "marginal", "complete" and so on?
I know, the answer lies in the source code. But unfortunately I am not 
able to read or understand source code.

Best regards Christine