Doesn't seem to handle default fonts properly

I've installed the module, very easy, everything fine. My first attempt was installing it on my hosting service, where I don't know what path to put in to find the fonts (I'll have to ask). So I just left the fonts path blank, and I come up with the problem that the characters produced in the picture often seem to be cut off at the top, so that they are impossible to read.

I have also tried this on my workstation (W/XP, French version), and get the same result (unreadable characters), with the following configuration in the admin > settings:

Number of fonts found: 0
GD Version: bundled (2.0.15 compatible)
FreeType Support: True