Clockwork's Level Calculator has, for the better part of ROBLOX's lifespan been a de-facto gauge of a person's experience for as long as most people could have possibly remembered. It's declined in popularity, but you can still see some ROBLOXians' blurbs mentioning their level (Usually as something of a "badge" of veterancy or someone's individual progress marker for ROBLOX experience).
It doesn't take too much of a rocket scientist to work with the Level Calc. Punch in the numbers from your profile, and the machine spits out the level so you can flaunt it to everyone who had the (dis)pleasure of viewing your profile. The fact of how easy it was to just to find out the "worth" of your ROBLOX self, official or not was more than enough of a sale to most people when it first came out.
Clockwork's Calculator, while very widely used by users to represent their relative popularity, has been criticised as being inaccurate for specific users that, while having a high amount of statistics in one area, such as knockouts, lack an equally large amount of statistics in a sector, such as place visits. This means that only users that have tiny amounts of every statistic may have a high level.