Guy's Behavior

What does it mean when the guy says "ditto"?

This guy and I have been talking back and forth for awhile. Sometimes we flirt while texting, but nothing too much and we hung out a bit, but not much at all. He still seemed to kinda be into me. He always said that he loved talking to me and never liked me saying good bye or good night if we were going staying awake.

Anyway, I didn't text him for about two days and when I tried texting him today, he just didn't seem like he wanted to say much. I stopped replying after his "yup!"

I sent him a text saying good night and have a good day tomorrow, his reply?

"Haha, ditto!"

Does this mean he has moved on? Or that I am annoying him...?
What does it mean when the guy says "ditto"?
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