I think it includes spaces but honestly, I have never written one that big. The ideal size is around 100-160. This gives a ship of your site but does not help in where you rank in Google.
A space is a character to a computer and has an ACII value of 32. Not counting spaces would slightly add to the complexity of the length checker and would really serve no useful purpose. So, it is HIGHLY DOUBTFUL that spaces are ignored.
Google increased the limit to 320 characters last year from 160 characters. Search on Google and you will find out.
I am talking ideal not limit. A short clear description is best. https://support.google.com/webmasters/answer/35624?visit_id=636841463415433849-3057859440&rd=1#
i think there is no word limit as such, but keeping it short will be easy for search engine to comprehend while indexing your web pages and content inside it.
Meta Description length is 320 character with including space and I think you can use the last 250 characters.
Here's a helpful tool (I have no connection to the tool; I just use it): https://www.portent.com/serp-preview-tool