

It's very common that Google, and other search engines, ignores the pre-defined meta description and uses one that they find more suitable.

Mobile and desktop results will display different numbers of characters due to the different layout and screen sizes of the result page in the search engine.

Try to keep the most important things, like your main keyword, among the first 120 characters. There is a recommendation though, to keep the meta description around 120 – 160 characters. Like the title there's no exact number of characters, but rather defined by pixels. Meta description on the other hand, which is the description of your website seen under the title and URL on the result page of Google and other search engines, is still very important. Meta keywords for example is long gone as a ranking factor. But for most webmasters it's only one meta tag that is really important for SEO now days. When it comes to meta tags there's actually quite a few of them.
