Optio S5i max memory SD card

Hi,
I have an Optio s5i and I understood that the largest SD card it would recognise was 2GB. But when I install a new 2GB card it first says that I have 600 photos available (implying that 2GB is available) but when I format it it drops down to 300. When I look at the card on my PC it only shows 1GB available - even if I reformat it again. It's not a faulty SD card as I've tried several different brands. Does the s5i have a max. of 1GB memory?