During my investigation of Sitecore xDB I tried several things and I found out that I want to increase a the value of a profile key programmatically. This question was helpful but it did not provide the whole solution. In some cases maybe you need this. It has been tested on Sitecore 8.2 update 3.
And the usage of the method is like the following.
After I hit the page I have the following entry in mongoDB, Interactions table.