Typing speed test

My mum told me that she like listening to me typing sometimes. So bored at home, I decided to take a typing speed test.

I just did one and the result is :

Your speed was 50 WPM with 1 mistake (adjusted speed 49 WPM)

Then I took a second test:

Your speed was: 53wpm. You made 2 mistakes.

Erm.. so I guess my average is 50 wpm but I can't continuously type like that for more than 10 mins.. my fingers will break!