You have 5 minutes to collect 0 targets? That's right! This mission lasts for 5 minutes and in those 5 minutes you are asked to kill as many Transmitting Devices as possible. Easier said: You don't have to kill any of them, but you can if you want. You won't get an extra reward for killing them (besides the extra EXP and spi the mob drops upon their dead, which isn't much).