you need to write property: value where you substitute property with text-align and value with center, you should not have the words property and value in your code
can you post the code and not use a screenshot please?
When you enter a code block into a forum post, please precede it with a separate line of three backticks and follow it with a separate line of three backticks to make it easier to read.
You can also use the “preformatted text” tool in the editor (</>) to add backticks around text.