I saw this as I was watching the news. It was the little bit of text that sits at the bottom of the screen and tells you what the story is about. In this case it was about the number of wildfires burning in our jurisdiction as we entered summer and the heart of wildfire season.
I can understand why someone would like to use a plus sign to show that they’re talking about a number greater than the one shown. You pick a round number to show where you are, then use the plus sign to indicate that the real number is between the one shown and the next higher round number. It’s also useful when one doesn’t want to put in an exact number for whatever reason. The plus sign is handy when you don’t want to say “more than.” When you’re texting on your phone, who wants to type “more than” when they can simply hit the plus sign? From there it slipped into speech as well.
The reason this caught my eye is the redundancy. It is essentially saying, “More than more than 170.” Why would anyone say that?