An older woman has given her number to me. What should I do?

Ok, so the other day I was at work and this lady came in three times. I smiled at her the first couple times and said hello - nothing more than the usual. The third time I wasn't in the shop so she left a note with my colleague and said it was for me.

My colleague proceeded to give me the note and I texted her a couple days later. She explained that she had wanted to give me her note the second time she came into the shop but chickened out.

Im 22 and im guessing shes 28. The note included more than just her number so I'm wondering whats going on haha? Is she aware of my age? I dont think I look that old haha.