In Govnah, the first value is used PHYSICAL MEMORY.
The second value is used VIRTUAL MEMORY
PHYSICAL MEMORY = RAM
VIRTUAL MEMORY = Swap drive
720 / 0 MB
You are using 720mb of available 1024 mb RAM, and 0 mb virtual/swap memory.
Virtual/Swap memory only is used when you run out of RAM.
720mb may sound like a lot of used RAM but Linux works to use up almost all of your available memory all the time, so apps load/run quicker.
It doesnt work like Windows, so unless your device is sluggish, using up a lot of RAM in linux is a good thing, its keeping many often use tasks in RAM so they are still there when you need them.