Footsteps on the Uninhabited Second Floor of Grandmother's House

Bump, I love these simple but true-to-life situations. In my grandmother's house, which was in something like an urban-type settlement, there was an uninhabited second floor, it was left a bit unfinished, and they just stored boards and other forgotten stuff there. So I was about 9, in the house were me, my grandmother, and my great-grandmother (her mother). Grandmother sleeps in the bedroom, and my great-grandmother and I are in the living room. I'm falling asleep and I hear what sounds like someone running around on the second floor, and by the sounds, something small, like a child or something. At first I thought, well, who knows, the house is wooden, the boards could shrink from the temperature, all that. But the sound was actually moving, sequentially. First above me, then it "ran" off somewhere into a corner of the second floor, then along the wall to another corner. I bricked myself pretty good, and I ask my great-grandmother, like, are you asleep? She says no, so I asked, what are those sounds on the second floor? Expecting her to somehow reassure me, I was pretty fucking shocked when she, completely calmly, and even sort of with warmth, like about some old acquaintance, answered "Aaah, that's Vanechka)". I didn't sleep the whole night after that, damn, it went on for another 7-10 minutes, but then there was one loud creak, in one spot, like someone jumped, or something, and it stopped