Having recently configured a number of venues in vSPoT I have experienced some problems with reading the Access Point numbers on the annotated radio map image.
This makes assigning the mac addresses of APs to Access Point Locations quite difficult, especially for large maps.
My solution has been to open the annotated file in Photoshop or Paint.net, hover over the AP locations and match the X/Y co-ordinates in the image to the X/Y co-ordinates supplied on the Access Points config page.
It's not a great UX and could easily be imporved by a larger font, AP icon and different colours. Maybe adding an outline to the text in the image would also help as black text crossing over black colours in the radio map do not show up well at all.