Sin means literally to miss the mark, so archers who missed the target sinned. If your boss says you need to be at work at 9:00 and you show up at 9:15 that's a sin to your boss. Exceeding the speed limit a sin to whoever set the speed limit.
Measuring sin is a little complicated, perhaps. Since we all inherit sin as an environmental sort of factor, our individual sins, no matter how trivial or extreme, are from the same place, so in that since equal in a sense. So inherited sin is like a child who isn't being held responsible for a specific sin but suffers as a consequence. Environmental, if you like. Then there is sin in a more direct sense. Various laws are given throughout the Bible that apply to specific people at specific times. Adam's was simple. Don't touch the tree or it's fruit.
The Law of Moses (600+ laws) was given specifically to Israel from it's reading by Moses to all the people and their acceptance until the law ended by being fulfilled by Christ. Essentially it was created to educate them. To the presence and effect of their sin, to their inability to keep it and therefore a need for salvation. So they weren't able to keep it. They had to have temporary sacrifices to teach them of the possible absolving of sin and the more perfect permanent sacrifice of a messiah who would deliver them from it's temporary harmful effects after they died, sin was removed and they were resurrected.
