This is how V-Grooves are cut into PCBs. V-Grooves are half-cuts into the PCBs that allow them to be snapped apart easily. Minimum V-Groove cut length in generally 8cm due to machine cutting length. V-Grooves must be cut across the entire PCB length, it is not possible to make short internal cuts.
This is from our PCB documentation at http://DirtyPCBs.com/store/pcbs/about check it out for more PCB manufacturing details.