If a girl give me her number is she at least interested?

Okay I know it sounds like a stuPid question but girls are so hard to understand. Anyways this is the story. It was about the end of the school year and I asked this girl to sign my yearbook and she wrote a good paragraph and stuff but she gave me her number at the end. So last day of school I go to say bye and that I'm not coming back and she says "keep in touch". So does she like me, or is she atleast interested?