Yes, reading the
Wikipedia article on SD cards, I see that you are correct. It appears that the original SD standard is only "truly" standard up to a size of 1GB. Various manufacturers have "extended" the standard to support 2GB and 4GB cards, but done so in different ways that different devices may or may not recognise. The SDHC standard is again a true standard, theoretically supporting capacities up to 2TB, but as yet relatively few devices support SDHC - the Reader does not.