For me they work fine. Probably you misunderstood the way they work.

The clip size is 3 bullets and what the game does is count the bullets in your weapon and the reserves you got. The reserves are always something divisible by 3 as you can only reload clips completly and thus losing bullets left in your old one.

So 3/6 means 3 bullets in your gun + 2 clips of 3 bullets reserve.

Hi yes Lamo is true. The way we think of clips is that in the real world once you change your clip you lose the remaining ammo in the previous one. (like if you throwed them away in the heat of battle). Anyway be carefoul when reloading since every bullet is importiant and should not be wasted.
Best regards

how to reload?

Press "q" to reload