Tom,
It took me a while to get my head around those settings, too. When it says 1:50 it will use that setting when the scale being used is LARGER than 1:50. 1/4" scale, for example, translates to 1:48 so it'll use the 1:50 settings when using 1/4" scale (1:48 is a LARGER scale than 1:50). 1:100 settings will be used for 1/8" scales, since 1/8" translates to 1:96 (1:96 is a a larger scale than 1:100).
As for setting the parameters, what I do is
1) Set the parameters for the zone in Options/Element Attributes/Zone Categories
2) In the model, temporarily change the zone I want to update to another zone category, then change it back to the one I really want to use. The updated parameters should apply.
Sometimes I found that this doesn't work if you only temporarily change the zone to a different category that uses the exact same default stamp (e.g. if they both use Zone_Stamp_2_18). So I make sure there is at least one zone category using a different stamp.
I try not to change parameters within an individually placed zone, unless I know that what I am changing is just a one-time thing.
Hope that helps.
Bill Szustak RA
Principal, Springboard Design
ArchiCAD 25, macOS Ventura 13.4.1