Airflow in grams/second.
See page 56: http://www.accessecu.com/support/st-dbw-userguide.pdf
You may want to look at a streetTUNER guide for your model of vehicle for more precise descriptions. Some things vary slightly from model to model
Example: DBW DAM is .05 - 1.00 in .05 increments, while cable throttle DAM is 1 - 16 in increments of 1.