Deleting items on the IDL

I managed to grow 3 of the same items, and I only wanted one. I deleted the item (thinking just one I would go away) but they all disappeared.

I have 3 more of the same item and I don't know how I can get rid of them. Does having this many of one item add up to the maximum amount I can hold? (holding 10 of a single toy +10 different toys=20 toys)

I don't know if this contributes to the maximum. But I know, having more than one of an item annoys me too.

What I do is go to the Donuts Park (in the afternoon but not the evening) and sell my items at the Tama Market. When you get to the Tama Market, you'll be greeted by someone like Mamametchi of Mamamemetchi. Then you need to select the second option (sell) and a few categories will be introduced to you. Choose the category that your item is in, and then select the item you'd like to sell. This way, you can get rid of extra items and get money for them!