My most recent projects have involved pausing my print at a specific Z-height and changing filament. It's a feature of the Sailfish firmware that I really enjoy. However, as I just learned, if you want to be precise on which layer actually prints before changing filament you need to be a little clever about the use of the tool.
The "Pause at Z-Pos" works like this: Every time a layer advances it check if it's at or above the pause-at position variable. That means if you set it to stop at at 2mm, it will pause when it moves the Z platform to 2mm before it prints the layer at 2mm. This gets even more confusing when using a layer height that doesn't make for happy math like 0.15mm, like I do.
If you want to be sure that the layer you're pausing at is printed before pausing you need to set your pause layer 1 layer height higher than you want it to actually pause at. Of course each project will have it's own oddities and sometimes that won't work as well as you'd like. But it's good to keep this in mind.