What is the effect of increasing or decreasing Authentication & Accounting interim-update time ?
/ppp aaa
set interim-update=5m
This is not Mikrotik-specific stuff, you could have just google before asking. Even wikipedia knows what RADIUS interim updates are. And it is not applicable to authorization, by the way, it is purely accounting-related.
You just set time in hh/mm/ss which set interval that router send accounting updates to radius server!