Correct settings for zones?

[Cylindric]

When I created my first camera, it had no zones. I added a zone and it all seems to have worked fine (see my other post in the announcement post)

I have now created a second cam (actually to the same device) and it started with one zone automatically, but it was an odd triangular zone. The Zone list shows it as 100% coverage, even though it looks like a triangle (0,0 - 639,0 - 639,470)

If I go in to edit this zone, it keeps complaining that:

You must specify the minimum alarm pixel count
You must specify the minimum filter pixel count
You must specify the minimum blob pixel count

Default settings were:

Name: All
Type: Active
Preset: Choose Preset
Units: Percent
Alarm colour 255/0/0
Alarm Check Method: Blobs
Min/Max Pixel Threshold: 25/blank
Filter Width/Height: 3/3
Zone Area: 100
Min/Max Alarmed Area: 0/0.05
Min/Max Filtered Area: 0/0.05
Min/Max Blob Area: 0/blank
Min/Max Blobs: 1/0

(See http://www.hanfordonline.co.uk/archive/zm-122zone.jpg)

I'm not sure what "sensible" values are for these fields, so can't really make them up.

[Cylindric]

Ah, I just found that I have to load a preset first, then it seems to work.