I created an extension and published it 2 days ago.
On the Web Store it says that there are 10 users, but if I look at the Google Analytics that I installed on my extension it says "305 Users, 604 Pageviews" etc, and if I sort my audience by city, I get a large array of locations and the number of sessions is very even across 20-25 cities...
So my question is, how accurate is the web store with showing the amount of users? Perhaps a lot of my users removed the extension, but even so, I'd expect more than 10 stuck around.
As your extension is still fairly new it may take a day or two before you are seeing numbers that reflect what you are seeing in Google Analytics.
Per the Google: https://support.google.com/chrome_webstore/answer/1154142?hl=en
The number of users includes everyone who has ever installed your item in the store, so it is likely greater than the number of weekly installs.
If the number of users is less than the the number of weekly installs, this may indicate that users are uninstalling your item.
These user count is supposed to update everyday but it's not always reliable.
The developer dashboard does track the total number of installs and impressions but even then it's only for a limited time period (3 months) and it's sometimes unreliable as there are certain outages where you won't get any data back.
A more accurate way would be to add a listener (chrome.runtime.onInstalled) for the install event and trigger a tracking beacon accordingly. Source: https://developer.chrome.com/extensions/runtime#event-onInstalled
As @Xan stated earlier using google analytics or something similar is your best way in determining the "actual" number of active users (daily, weekly, monthly, etc.) Simply take the values listed on the Chrome web store with a grain of salt.
On a related note a useful tool I've found in quickly seeing total number of "users" as per Chrome Store is My extensions. It helps with getting notified of user reviews as well.