There's also a thread somewhere explaining how to change the config lines yourself, which is what the "mod" is.
It is meaningful though, it means the game didn't save, so be sure that wasn't the last message you got before you shut the game down or you're going to lose your work.
It's this section, in the XML file:
<PopupMessage>
<BasicValues>
<PopoutTimeInSec>0.3</PopoutTimeInSec>
<DistFromTop>614</DistFromTop>
<DistFromRight>-10</DistFromRight>
<StackedDistanceX>200</StackedDistanceX>
</BasicValues>
</PopupMessage>
This is the line the "mod" changes, and the value it changes it to (I forget default): <DistFromTop>614</DistFromTop>