Board Game Arena

Hi,
How does work UNIQUE DECADES in solo mode ?
I was surprised to not to be able to play "1972 red", while I hadn't any 197X card in my entire board. I had to place it on a negative space.
This game shows my case : https://boardgamearena.com/6/exhibition ... =726537568

See the specific rule for each showcase size (6, 4, 3, 2 or 1 card showcase) at the question mark '(?)' at the right-upper corner of the showcase.
(At phones push the question mark and keep it pushed a few seconds.)
At the solo game you see there "With 1 player, only the 40s and 50s are allowed.".

- The idea of that 2-spots showcase is: Different decades, different to other players (you want an original exhibition).
So with 5 players, if all players fill their 2 spots, there will be 10 (5x2) different decades in it, so all 10 different decades.
- Special is: At first you have much (all) choice, no need to place a card there at the start? But once these spots get filled by many players, so the remaining allowed decades become more limited, it becomes a fast race to place cards in time before your options get very limited. Interesting showcase in 5 player games.
The lower number of players, the easier it is to fill these spots with that rule. Therefore the allowed decades are limited for less-than-5 player games:
With 4 players: The 00s and 90s decades aren't allowed, so 10s, 20s, 30s, 40s, 50s, 60s, 70s, 80s are allowed.
With 3 players: The 00s, 10s, 80s and 90s aren't allowed, so 20s, 30s, 40s, 50s, 60s, 70s are allowed.
With 2 players: The 00s, 10s, 20s, 70s, 80s and 90s aren't allowed, so 30s, 40s, 50s, 60s are allowed.
With 1 player (solo): The 00s, 10s, 20s, 30s, 60s, 70s, 80s and 90s aren't allowed. So only the 40s and 50s are allowed.

That's extremelly clear Thank you