Bonus Armour

Do abilities which give extra resistances (for example, those of , , and ) count as base armour or bonus armour? I was against a Poppy last game and both of us had full build. She had 275 bonus armour and I had 45% bonus armour penetration and 7% overall armour penetration. This put her at a grand total, under 40% health, of about 450 armour. It was a TON of armour, and I was wondering how effective my Last Whisper actually was in this situation, while I sensually massaged her back with acorns.