The default assumption isn't that Threshold be 30, it's that threshold*recovery rate = 240. The data file is set up the reverse way around, with threshold being 240/recovery rate. This means that, with the default settings, you can increase/decrease Recovery Rate in the Attributes tab and it will automatically adjust Threshold to the the appropriate multiplier.
If you want to change it from the default you would simply replace the entire contents of the basevalue() tag with your desired number or formula.
Version=3
* The version information above MUST be the first line of the data file
Code:
[ATTRIBUTES]
Threshold, maxscore(240), minscore(1), display(no),
basevalue(50)
Recovery Rate, maxscore(240), minscore(1), up(0), down(0), step(1), display(no),
basevalue(8)