Just wanna double check. I hv iMac model 24" (early 2009). If stated on tis web max memory can go is 8GB. Wonder if this model can support up to 16GB (2 slot of 8GB).
In that case, Apple is right. The Early 2009 iMac only supports 8 GB of RAM. You can buy more RAM at OWC or Crucial. Late 2009 and newer iMacs support 16 GB of RAM.