What is the burning speed in MF4

[mikeb]

I am using Verbatim 8x discs with MF4, when it burns it shows 12x although I set it to 8x. I have seen that other people are getting the same problem, but does anyone know if it shows 12x by mistake and burns at 8x or is it actually burning at 12x. I was asking this as it seems to burn the discs ok without any error messages. If the discs are being burnt at a higher speed than 8x could this cause a problem when being played back on my customers players later on.