Trouble with properties

I seem to be having a little trouble with properties in a script I’m writing (with the purpose of turning it into an addon). Whenever I run the script and it registers, the properties I defined are not being set to their default values but instead to what they were last time I ran the script, even though it was unregistered and the properties deleted. Here’s how I’m defining the properties:

bpy.types.Scene.aVis_NumBars = bpy.props.IntProperty(name = “Number of Bars”, default=64, min=1)

and here’s how I’m getting rid of them:

del bpy.types.Scene.aVis_NumBars

It may be worth noting that while the script is running I have these properties linked to a panel so that they can be changed. I still don’t understand why they’re not being reset to their default values though. I have tried closing and opening blender, that didn’t work either.

Is this an issue with how I’m using/defining the properties or is it something completely different?
Thanks in advance!