This is normal if you are using Inventory solution. When the hardware inventory runs it picks up the fact that the machine is actually a virtual machine and reports the information back to the Notification Server.
You have a couple of options you can disable the conversion of computers to a virtual machine. However most companies like to know what computers are actually virtual machines. The other option is to get a count of your VMs & computers seperately.
Count of VMs
select count(*) from Inv_AeX_VirtualMachine
Count of physical computers
select count(*) from vComputer
where name NOT IN(
select i.name from Inv_Aex_VirtualMachine vm
join item i on i.guid = vm._resourceguid)
HTH