How do my activity readings relate to Citrate Synthase?

I've got three unknown proteins.  I found the concentrations of each through BCA assay.

protein type
U1: nuclear genome
U2: mito
U3: mito/nuclear genome hybrid

We did a citrate synthase assay.  For each unknown we measured activity on our spec using 5uL and 10 uL.  We only had time for one reading at each volume for each unknown(6 readings).

As the volume of protein increased for each unknown, the ABS/sec also increased.  What does this mean as it relates to the citrate synthase?  What does it mean when the volume of a protein increases in an activity reading and the ABS/sec rises, and how does this relate to the synthase? increases