Acetate concentrate type

There is no 2.5K concentrate available that I have ever seen.
To spike a jug of concentrate up to 2.5K would require you to weigh the correct amount of K additive and add it to the jug.
I only know of additives from Edlaw and they are powdered. I think there used to be a liquid additive years ago but I have never heard of anyone using it.

Now if your question is more theoretical.....
Since you mentioned conductivity you already know that the machine can't differentiate what ions it is measuring. It can only measure all of the ions together.
All Fresenius machine models use volumetric proportioning meaning that regardless of chemical composition of the concentrate and bath selection on screen, it proportions the same volume of concentrate, water, and bicarb. This will result in the dialysate having the composition that it should have. In THEORY, you may see a difference in the conductivity but in your example, 0.5 mEq/L difference probably wouldn't change the conductivity. Changing the bath selection only alters the conductivity alarm limits to take into account the different ion content.

The Braun and Phoenix machines proportioning are servo-controlled meaning they will proportion more or less concentrate, water, and bicarb in order to maintain the desired conductivity. These machines are set for a conductivity, not a concentrate composition. If you alter the composition of the concentrate, in THEORY you may need to alter the desired conductivity.

To show your example on paper (screen), you can calculate the theoretical conductivity with the formula: (Na + K + Mg + Ca - 6)/10

A standard 2K/2.5Ca bath would have a theoretical conductivity of 13.65 mS/cm (the machine would round this up to (13.7 mS/cm).
Your 2.5K/2.5Ca bath would have a theoretical conductivity of 13.70 mS/cm.