Factorio Forums

In my case, decider combinator return not matching signal, and not first matching signal as described in wiki.

This looks like a second part of 116902 - basically due to changes of decider logic for 2.0 and ability to have multiple conditions, output "anything" is no longer tied to a specific signal that made it pass on the conditions side through an anything condition. You can workaround this by having "Each > 25 output Anything" which will internally check which signals on input are passing the conditions and it will output only one of the passing signals.

I agree that this is not working correctly as per the description in the tooltip.
"Output the first input signal, or the first signal that passed all conditions, respecting signal order..."
Even when using the workaround "Each" for the input, the "Anything" signal does not appear to respect input order.
Based on the information in the tooltip, I would have expected either Iron Gear Wheel OR Battery to pass the condition AND be "the first signal that passed all conditions" depending on whether Input Signals is listed first in, last out or first in, first out - the selection of Concrete was unexpected. When switching signal conditions, or removing Concrete from the inputs (in this case Ice gets selected at this point), then reapplying the signal conditions or re-adding Concrete to the inputs, it is once again selected as the pass-through from "Anything". After some testing, it appears that the order is as per the "Set a Filter" when applying to a Constant Combinator (or similar) organised by Tabs first, Items next as removing the signal inputs in order of next seems to follow; i.e. Concrete -> Ice -> Steel -> Solid Fuel -> Battery -> Iron Gear Wheel, removing Concrete will yield Ice as the next output, removing Ice will output Steel and so on (assuming they have met the condition, in this case > 1000 items). This appears to match the order of Logistics Tab, Concrete, No more Logistics Tab, move to Production Tab, No Production Tab, Move to Intermediate Products, Ice, Steel, Solid Fuel, Battery etc. (This may not be 100% accurate, but appears to the case from in-game testing).
I think the easiest solution is to update the tooltip with the current behaviour if the current behaviour is intended. Double checking the Factorio Wiki there is a line that mentions this behaviour which could be added (i.e "Outpur first input signal (precedence as per Factoriopedia)".

Hope that all makes sense and is constructive. It is certainly not game breaking, but was confusing for a while!