These numeric values are used to indicate how a player is perceived by a specific faction.
These values are defined globaly by the FACTION_STANDING_LABEL(x) variables, locale specific.
It's better to use them instead of relying on the hardcoded values above.
/script x=4; temp=getglobal("FACTION_STANDING_LABEL"..x); message(temp);
Gives the message "Neutral".
The API page from which this was moved credits Saien with providing the first documentation on these numbers.