Yes, your voltage reading is a little low because of the batteries. Your current reading will not be correct either if you do not have 2 X 3.6 volt batteries.
You really need to stop thinking about voltage, and measure the current! The current is what is important, along with SUPPLY voltage. You can put up to 37 volts into that driver and your LD will be fine. It will take what ever voltage it needs, as long as the supply voltage is over 7 volts.
So...
* Proper test load
* Proper supply voltage
* Check CURRENT
That's it! Then just make sure you discharge the cap before you connect your LD...
Jay