What does it mean when a girl gives you her cell phone number unsolicited?

I introduced myself to a girl in one of my cles. She holds a position in student government, and I had a request on behalf of a club of which I'm a part. She wanted to think over the request, so we decided that I would email her more information about the request. She wrote down her name and email address on a piece of paper, but before she gave it to me, she also wrote down her phone number and specifically told me that it was her cell phone number. I got the feeling that she hadn't planned to write down her number—like it was a bit of an afterthought. However, I really don't know her beyond having seen her in a few of my cles, so I don't have any basis by which to judge her behavior. I just thought it was sort of odd that she gave me her number when the business we discussed didn't require it, and I also thought it odd that she noted that it was her cell phone number when that wouldn't really matter if she were giving me the number for the business we discussed. Do you think she gave me her number because it was expedient for the business at hand, or do you think that she was trying to hint at something else? Help!