This doesn't matter. BCP, as all miners, is based on probability rather than actual work done. So you could set it running for 5 seconds and earn a shed load (very unlikely), or run it for 5 years and earn nothing (also very unlikely). The indicator bar is purely based around estimated payout to give you an idea. Closing the browser 5 seconds before it reaches the end has absolutely no baring on whether you get any payouts or not; all it does when it gets to the end is go back to the start.

This is all explained very clearly in the site's own FAQ.