interesting. but set what to 50%?
I'm pretty sure that I used to use it as a gauge/timer while doing my tech and trimix training. I just ignored the deco indications. I don't recall specifics though...was it continually beeping at me? Did I mute it somehow? not sure
If you are talking about the Aladin Pro Nitrox, you can set the Nx %.
But for me it was long time ago, in the last century
I was doing Tx and multi-gas dives with printed tables but still, I had this Aladin but no electronic gauge like the round Uwatec.
By setting it at 50%, you could change the computer to a good gauge and just follow your tables.
Otherwise, the computer would lock, and we would have had to remove the computer under water, just before surfacing, and leave it dangling at the end of a line at 5M. Once on board, we were "fishing up" the computer to check if it has cleared the deco calculated for a single gas.
Of course, to do this nowadays, it is stupid and useless as cheap gauge-computers are easy to get...