Based on the information provided by Sony and AMD, we can estimate that xbox one is overtracked, by how much? depends of sony shipments and what does near 30m means.
Assuming full 30m shipped according to AMD and 19.5m shipped for ps4 (1m on store shelves), that leave to:
30m shipped - 19.5m shipped for ps4= 10.5m shipped for xbox one
11m sold through VGC - 10m sold through for xbox one ( assuming 500k on store shelves, I know it's much more)
= 1m overtracked
Assming AMD 29.5m shipped and 19m shipped for ps4:
29.5m - 19m ps4 shipped = 10.5m shipped for xbox one, assuming shipped = sold.
11m VGC - 10.5m = 500kovertracked for xbox one.
Assuming ps4 shipped = sold that means 18.5m shipped
29.5m shipped - 18.5m= 11m shipment for xbox one
It doesn't matter how you look at it, you will always find an overestimate numbers for xbox one, it will depends how much sony shipped and what does near 30m means.
