I am using this plugin in many wordpress based websites. But I noticed something wrong with the titles.
The fact is I respected the recommended lengh (70 characters) and never exceeded that amount.
However, when google indexed my pages, the titles were wrong.
After investigating a bit, I found google is showing the titles that fit in 500px width. I also noticed that google uses bigger font size (18px) than the plugin's Snippet Preview (16px).
This is why the title seemed to be ok in the preview, using smaller font size allowed to put more characters. After that, when google indexed it, did not fit all the characters, because of the bigger font size they use.