There is a contradiction in the following statement.

The tradelist decklist count says.

How many cards you need in ALL decks (same for built and ideas) (The maximum count from any of your decks - it assumes you are willing to use the same card in multiple decks.)

I'm not sure I see a problem here.

It's incorrect because it lists the maximum you need in all decks. So if you have a playset in 2 different decks. It will list 8 cards.

Hence there is no need to assume you are willing to use the same card in multiple decks. Or it should just say 4 max (because the playset is used in multiple decks)

Ah, I see the issue now. It depends on the "I am sharing cards between built decks" option in the account settings. For me, I have it checked, so the tooltip is accurate. For you, you (presumably) don't have it checked, so the tooltip is incorrect.

Sebi, there are 2 possible solutions that I see:
1) Change the tooltip to be generic: "How many cards you need for ALL decks (This depends on whether or not you are willing to share cards between decks, which is set in the account settings.)"
2) Have two different tooltips that are displayed based on that account setting.

I indeed have it unchecked.

Ah, I understand now, thank you both for the clarifications. Will make the tooltip a bit more generic (to come the next big release).