How many "Charge Offs" can a company put on a single debt?

A while ago I took out a loan and couldn’t pay it off due to loosing my job. I got another job, and before I could start making payments, a collections agency called me up about the loan. I paid it in full through them and thought nothing of it back in 2015, (they stopped taking payments from my bank account, so I assume that it was paid off). Now I’m looking at my credit score five years later and noticed that there were more than one Charge Offs on this debt. To be exact, there are 28 charge offs on this one debt, and I’d like to know if this is even legal. The loan was from The Home Depot/Citi Bank of North America, if it matters.

Here is a picture of my credit report from Experian: