Here is what I came up with for the ipod video 5.5 it is a good solution in that when its close to zero the sound level is low enough that is not useful any more and when its at 50 it pretty much is half the volume (actual sound coming out of speakers- not just the number) and the 100 is 100 lol thats hard to mess up. lastly, MAX is those final 6 clicks above 100 that rockbox will not let you assign a value for, so I just wrote max. I have been using this for a long time now and am very happy with it. It is much better then seeing the volume represented in DB which no one I ever met understands... but 0 to 100 everyone understands. hope this helps some people out there who are writing their own WPS.
%?pv<0|0|0|0|0|0|0|0|0|0|00|00|00|00|00|00|00|00|00|00|00|00|00|00|00|00|01|02|03|04|05|06|07|08|09|10|11|12|13|14|15|16|17|18|19|20|21|22|23|24|25|26|27|28|29|30|32|34|36|38|40|42|44|46|48|50|52|54|56|58|60|62|64|66|68|70|72|74|76|78|80|82|84|86|88|90|92|94|96|98|100|max>
(the above is all one line in your wps)