In general, storage capacity depends on which image size and quality you have selected.
For your information, here is the number of images recordable in a 8MB Compact Flash in the respective image size and quality. Since the image size may vary depending on scenes and subjects, these are approximate values only.
Economy: 13/20/26/51
Standard: 8/12/18/40
Fine: 4/7/11/28
Super Fine: 0/1/2/8
(Pixel Size: 2048x1536/1600x1200/1280x960/640x480)