savage species natural armor question...

[00durrin]

in the advancement for monstrous races in SS I'm not sure I understand the natural armor bonuses.
for example a troll gets the following natural armor bonuses at the corresponding levels:
1: +2
3: +3
5: +4

does that mean at 5th level he has +4 to his natural armor TOTAL, or +9?
I was thinking +9, but that gets powerful really quick...
I was thinking this because the stat bonuses obviously accrue...what would be the point of +2 str at 3rd level and +2 str at 7th if they didn't stack? maybe natural armor is different because it is a named bonus?

 

[kreynolds]

in the advancement for monstrous races in SS I'm not sure I understand the natural armor bonuses.
for example a troll gets the following natural armor bonuses at the corresponding levels:
1: +2
3: +3
5: +4

does that mean at 5th level he has +4 to his natural armor TOTAL, or +9?

+4. At 11th level, the Troll is fully matured, with 6 hit die and a natural armor bonus of +7, just like on page 180 of the MM.