OSPF Default Routes IA vs N2

You can see explanation if you issue
sh ip route
Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP
       D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
       N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
       E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP
       i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS-IS inter area
       * - candidate default, U - per-user static route, o - ODR
       P - periodic downloaded static route

IA code - advertised into OSPF stub or not-so-stubby area by ABR (reason: LSA type 4 & 5 are not permitted in stubby areas)
E code - external route advertised as type 1 ot type 2 external route into backbone or non-backbone area (normal or stub), except external routes advertised into NSSA
N code - external route advertised as type 1 ot type 2 external route advertised into NSSA (converted to E1 E2 by ABR when advertised to backbone area)

I believe this : IA 0.0.0.0/0  can show wherever LSA type 3 is not permitted , Like Totally Stubby and Totally NSSA

N2 0.0.0.0/0 : can show wherever LSA type 5 is not permitted , probably in all types of Stub areas.... such as : Stub, Totally Stub, NSSA, Totally NSSA

LSA type 4 and 5 are not permitted in stub or totally stub areas (including nssa stub/totally stub areas).

LSA type 3 are not permitted in totally stub and totally nssa, but in stub and nssa areas LSA type 4 and 5 are not permitted - only way to advertise route is to advertise it as summary route LSA type 3. That's why in stub areas ABR is injecting default route as LSA type 3 (in totally stubby and totally nssa areas, only special LSA type is permitted as default route (but in documentation is not mentioned as LSA type 3 - since LSA type 3 is not permitted)).*
   - Since route is marked as IA - that supposed to meany that it is - IA - OSPF inter area (LSA type 3)

N type related to LSA type 7. Reason is the same as above, LSA type 4 and 5 are not permitted in stub or totally stub, so, N type is related only to NSSA and totally NSSA (LSA type 7 is permitted only in those 2).

E type default route can be found in normal area types.

You can find nice visualization - OSPF Areas and LSA Types

*Edited imprecise statement.

I believe I should have noted them this way :

O* IA 0.0.0.0/0    :  ABR will inject this when LSA type 3 cannot make it  to  Stub , Totally Stub , Totally NSSA  areas

O* N2 0.0.0.0/0 :  Not Sure --- I saw that when you configure NSSA Default Information Originate on the ABR

N2 should not be injected by ABR, but ASBR.

in which situation the Administrator should use :  NSSA Default Information Originate

Thank you