Each group of measures (e.g. Length, Weight, Volume) has its own identifying gesture performed with the first hand. The appropriate system of units (Metric or Imperial) is indicated by the second hand.

a)  For the Metric System as thumb, first finger hand, thumb and first finger pointing downward and fingers fwd-inwd.
b)  For the Imperial System as first finger hand, back forward and pointing inward.

In both cases the increasing magnitude of any one unit is indicated by touching (1) tip of 2f. of 1st hand, (2) !st wrist, (3) centre of 1st forearm (4) ctook of 1st elbow.

All signs are in the dictionary.