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I agree, with @enjieneer. Wouldn't you want to sell for a price that is "greater than or equal to"?

It's like this.
You want to sell at 9
And you chose Conditional Greater than or equal to but you didn't put the same price.
You put instead 11.
Now your Coins will sell if the next executed trade is greater than or equal to 11.
It means 11 will sell before your coins set at 9.

I think t has something to do with the sell if it would cross your price or not first before your sell order gets executed.
You can read the condition on the last photo.