As to the PDF Guide on page 19:
How can I connect to the unused pins?
The analog pins (analog 0-5 also known as digital pins 14-19) are broken out in the bottom right corner.
Pin 2 has a small breakout since its the only truly unused pin
The remaining pins are not broken out because they could be used by the motor shield. If you are sure
that you are not using those pins then you can connect to them by using stacking headers when
assembling the kit or soldering onto the top of the header with wires, or using a "Wing shield"
So you should have access to pins A0 to A5 (enough for 6 servos). You might need to solder a pin header in that place before you can actually use them.
The wording "Pin 2 [...] the only truly unused pin" is a bit weird, but if you follow the link to the schematics repo and look at mshieldv12schem.png (which seems to be the schematic just as an image, so you don't need to install Eagle for viewing it) it shows the Arduinos pins A0 to A5 only connected to the pin header and nothing else. This tells me that they are actually free.