I work in tech support
Our salary is depends on the amount of closed tickets, like per day that's 20 tickets, everything above is will be end as an + to your wage

I found an unfair way to secretly increase the number of closed tickets so that at work I actually only worked for a couple of hours, the rest of the time, for example, I watched YouTube

I did it for a couple of months, now my boss found that out and sent me links to every ticket I duplicated
He asked what we'll do with it. I shortly answered "charge a fine", but he said "You think so?"

What should I do? Actually i'm in the process of employment into another company which offered me twice as much salary (i'll be system adminstrator) and planned to quit my current job in a week or two