You can specify a final height or apply a scale factor to selected objects. Scaling is done from each object's justification point, or you can specify the justification.

Command: TSCALE
Select objects: Use a selection method to select annotation objects
Specify justification to use as base point for scaling... [Existing/Start/Center/Middle/Right/TL/TC/TR/ML/MC/MR/BL/BC/BR] <Existing>: Specify a base point
Specify size change by [Scale (factor)/Height] <Scale>: Specify the value as a scale factor or the final height
Scale factor <1.2000>: Specify the factor to scale each object by
Or
Final height <0.2000>: Specify the height for the selected objects

See also: PSTSCALE