Adobe InDesign DataMerge multiple records do not fit a page

Dear Community, 

I need to produce some attendee badges. They are to be printed borderless on a pre-cut A4 paper (4x2 badges per A4 sheet). Each badge has dimensions 10.5cm x 7.425 cm.  That should be exactly 1/2 the width and 1/4 the height of the A4. However, it appears that Data Merge is not able to fit 8 badges on a page. Instead, it just adds 3 records vertically on each page. 

Any ideas what may be wrong? 

Thanks!