Of/in the order of something
Definition 1 of 2
Pro Tip 1/3Estimate Figure
Used when exact numbers are unknown, to give a rough estimate. 
The company's revenue is of the order of $10 million.
Pro Tip 2/3Imprecise Measurement
Indicates that the speaker is not committing to an exact measurement. 
The population of the town is in the order of 20,000.
Pro Tip 3/3Large Scale
Often used for talking about large numbers or amounts. 
Damages were in the order of several billion dollars.