Puissant (ability) and character development

There is some confusion here on how Puissant (Ability) affects the cost to increase a skill by a level.

Our multi-lingual scholar Zephyrum (an early fan of Fibonacci's translation of Hindu-arabic numbers) has both Affinity with (Artes Liberales) and Puissant (Artes Liberales), and at character creation spent 50 points on Artes Liberales.
The way we interpreted it, this would mean a score of 4 in the ability, the Affinity would raise the score to 5, and then Puissant would effectively bump the score up to 7.
Now Zephyrum is studying to increase his score in Artes Liberales, and we are undecided if the advancement cost should be based on the number of points already invested in Artes Liberales (ie score 5), or include the Puissant Ability (ie score 7).

Can anyone clarify please?

One of the arguments being thrown about is - Can a character have a (latent) Virtue Puissant (Ability) before learning that Ability?

The books tend to use Artes Liberales 5+2.

There's an important erratum to ArM5 p.48 Puissant (Ability), which answers your question:

Cheers

advancement is based on the actual score of 5, due to the erratum quoted by One Shot above.

I don't see why not. Mind you, that character would still be subject to the rules for "Abilities with no Score" from p. 62 I believe.

Why do we never have the errata on hand
Thanks

Though the the bit about "writing" does suggest its own question.
Zephyrum's score in Artes Liberales is the number of different alphabets he can read. Should it be 5 or 7?

7: they are definitely using the ability, not writing about it in a meta sense.

Bob

that's why our (my) SG's ArM core book is full of handwritten errata everywhere.. that makes it a LOT easier..