zones - area shows 0

[KeesW]

I've just started to use zones. I have a query that is so basic I am reluctant to ask it. Oh well, here goes. Archicad at work keeps indicating that my floor area (A:) on my zone stamp is 0. Archicad at home calculates area and fills it in correctly on my zone stamp. My area reduction option is set to 0.
Have I pressed a button somewhere or altered a setting without realising?
KeesW
AC9, XP Pro

[KeesW]

Please ignore the smiley on my previous post. I typed a colon and a closed bracket. The smiley looks silly and out of context.

[Erika Epstein]

Which zone stamp(s)?
Could you post screen shots?

[KeesW]

Erika
Thanks for your reply. I have re-entered them and they are now OK. It seems that selecting all of the zones with the marquee, and then changing the 'subtract areas' setting to zero, does not change all of the selected zones at once. Selecting them individually does work so it is now OK.
Kees