See the link in post above it is all there.

Total alkalinity is expressed
as milligrams per liter or
parts per million calcium carbonate
(mg/L or ppm CaCO3). A
total alkalinity of 20 mg/L or
more is necessary for good pond
productivity.

I have never heard of a reading less than 1 ppm. This must be an error. Get Todd to check and then post back.