tack on

Miyuki MiyabeのCrossfireを読んでいます。
"pyorokinesis" の能力を持つJunkoのところに見知らぬ人から電話がありました。
"Who are you?"
There was a moment's pause before he answered.
"A Guardian."
"A what?"
"Guardian. As in 'protector.'" With another teasing laugh, he continued. "It's okay, you don't have to understand. You will soon enough. I just wanted to let you know that we're impressed with the way you work." Almost as an afterthought he cheerfully tacked on, "And that you're very pretty. Okay, bye!"
The connection was cut and Junko was left, astounded and alone.
この意味の "tack" は知りません。辞書を見ます。
・Macmillan Dictionary: to add something extra, especially something that does not seem to belong to the rest: It’s a violent movie with a happy ending tacked on.
・Farlex Dictionary of Idioms: To add something on to something else. A noun or pronoun can be used between "tack" or "on." Miss, can I tack a side of bacon onto my order? If you kids keep talking, I'll tack another essay onto your homework.
・American Heritage Dictionary: To add or append something additional: The hotel tacked on a five percent service fee. I read my essay again and tacked an introduction on.