Figure captions are incorrectly numbered when I generate a book - How can I stop this?

I have a book with 22 chapters, each of which contains multiple figures. I want the figure numbering to match the chapter number (1.1, 2.1, 2.2 etc.). I am using series labels in the following format for my captions: <br />F:Figure <$chapnum>-<n+>. \t<br /><br />When I add all the chapters to my book, and generate the book, the figure numbers are all correctly prefixed with the chapter number, but the second part of the figure caption number seems to be based on all the figures in all the preceding chapters. For example, the first figure in chapter 5 should be 'Figure 5.1', but it is showing as 'Figure 5.447', as there are 446 images in total in the preceding chapters.<br /><br />How can I format the figure caption so that the numbering sequence (for the portion after the chapter number) returns to zero at the start of each chapter, when the chapter is intended to be part of a book.<br /><br />If the chapters are not part of a book, the caption numbering correctly starts at 1 each time.