Bug or Not

I participate in the Weekend Testing session where some passionate testers come together online and decide on an open source application to test. Then each one tests the application for an hour and comes up with a list of bugs, learnings, experiences and a lot of things which cannot be experienced in the office environment.

Last weekend, our mission was to generate testing ideas for the application Converber v 2.1.0. I somewhat deviated from the mission and started testing the application. Though later on I learnt about the term "Testing Idea" which meant "To think about scenarios/environment to test the application". During my Testing, I found a functionality which was very wierd and confusing.

Let me give you a small background about the application before arguing. Converber is an application which converts a given unit to some other unit of one's choice. In this application, there is a functionality viz. If you press "Ctrl+C", the result will be copied to the clipboard. The functionality worked fine except for one scenario which got me confused.

Here's the scenario:
My Left hand side unit is "centimeter" and my Right hand side unit is "decimeter". Now, 10 cm = 1 dm. So I entered 100 cm on the left hand side and got the result as 10 dm on the right hand side. Now I pressed "Ctrl+C" and when I pasted it, I got 10, which is as per the functionality. Now I tried selecting the left hand unit textbox viz. 100 and then pasted onto my editor and got 10. This is as per the functionality of the application but not something a normal user knows.

A normal user knows that if you select a text and press "Ctrl+C" then the selected text will be copied to the clipboard. But in this case, it sticks to the application specific functionality. So is it a "Bug or Not".