The term link: is a special operator, and you need to follow its syntax exactly - that means no space if you really want the operator function. When you include a space, you have turned link: into one of your regular search terms. You therefore get a higher number, because a true link no longer needs to be present - just the word "link" and the terms included in the domain name.
Here's the word from Google:
The query [link:] will list webpages that have links to the specified webpage. For instance, [link:www.google.com] will list webpages that have links pointing to the Google homepage. Note there can be no space between the "link:" and the web page url.
This functionality is also accessible from the Advanced Search [google.com] page, under Page Specific Search > Links.