# Everyone who is counted

"Everyone you count" or "Every man you count". They counted only the men.

# half a shekel of silver

"1/2 a shekel of silver." Translators may use a unit of measure that people understand and a round number: "5.5 grams of silver" or "six grams of silver" 

# according to the weight of the shekel of the sanctuary

There were evidently shekels of more than one weight at the time. This specified which one was to be used.

# twenty gerahs

"20 gerahs." A gerah is a unit that people used for measuring how much something very small weighed.