Please see WP:RS and WP:CITE.  Also, WP:V.  It is your responsibility to provide a suitable citation.  I have done so already, RIAA's own site.  While I have no doubt you are telling the truth, Wikipedia requires that information be verifiable.  I can provide evidence that Nickelback's album is certified triple-platinum straight from the certifying authority.  You can provide a less reliable source indicating that it is certified quadruple platinum.  However, since RIAA is the certifying authority, we have to use their figures.  Once again, it is entirely possible that you are correct.  In fact, it is likely that you are correct.  But Wikipedia's criteria is verifiability and reliable sources, and so I'm afraid that we need to stick with that source barring anything better.     