The Tenet "Shelter the True Oracles" add +1i on Mountain tiles.

However, if those Mountain tiles are exploited, when you click the corresponding City, they show +2i instead of +1i.

This is just an UI error and it exists in original game.

When I add "+1 CultureProduced" to River tiles or Resource Deposits using Mod Tools, this UI error appear in River tiles or Resource Deposits.

The first screenshot show the correct UI (+1i on Mountains), because I does not open the City panel.

But the second screenshot show the wrong UI (+2i on Mountains), as I clicked the City panel.