Why is this important?
This is important for SEO for the reason that when you search for something on a search engine for example Google, the first 60 characters is likely to be listed and anything else and any remaining text after that is likely not to be included.
Google typically displays the first 50-60 characters of a title tag. The reason this is a range rather than a fixed number is because it is actually the number of characters that can fit in a 600 pixel space that is counted rather than per character. For example some characters naturally take up more space. A character like uppercase 'W' is wider than a lowercase character like 'i' or 't'. If you keep your titles under 60 characters, research suggests that you can expect about 90% of your titles to display properly.
An exemption to this rule is brand or company names found at the end of the page title. These can be excluded from the character count since bookmarks and other locations will still display this information.
Why not count page titles based on pixels instead?
When creating a page title it is easier for a user to count the number of characters. Content creators usually have a flow or process to follow when creating content and the page title is usually the first element of the page that is populated. Having to calculate the pixel width and summarize this tend to break this flow as compared to simply keeping in mind the number of characters within a certain range. Content creators may not also be aware on how to calculate the limit in terms of the pixel width of characters.
How can I resolve this issue?
Limit the number of characters in the page title to below  characters
What topics do this checkpoint affect?
Can you explain how this checkpoint works?
This checkpoint checks the title tags and makes sure that the content inside the tag does not exceed 60 characters in length.