The Upwork system takes snapshots of your six-, 12- and 24-month history in the marketplace and calculates a score for each. The bestscore out of these moving time windows is displayed on your profile and updated about every two weeks. To learn more about this, please click here.
She asked how often it is updated, not how it is calculated... The answer to which is every 2 weeks, tomorrow is the next Update.
It is every second Sunday, at some time in the afternoon (UTC)
Ashley, I wouldn't hold my breath for a massive increase, your last job ended with the client knocking marks off for quality and skills, which usually goes with also reduced private feedback.
The only time I had a 4.6 (my lowest ever) my JSS went down 7 % (but the private feedback will have been considerably lower, after I essentially, in not so many words and slightly more diplomatically, called the client an idiot...)
Ashley, to the best of my knowledge, it's *always* updated every other Sunday. If you look at your My Stats page, right below the big circled Job Success percentage, it should show a 'Last updated' date.