file size difference between office 2007 and 2013 while using checkboxes

Hello

I made a workbook as a test that consist of 10 tabs, each tab has 780 checkboxes for a total of 7,800 check boxes on the workbook, the workbook has nothing else but checkboxes, now if I save this workbook under laptop 1 running office 2007 win 7 64 bit the file size is only 187KB, now if I save the same file on laptop 2 running office 2013 win 7 64 bit the file size is 2.85MB, I would like to know if someone know why this happens? again the workbooks has nothing else but checkboxes, no macros, no links, no unused areas, nothing.

Hopefully someone knows why

Both file extension is same or different.

Dear xcel50, Excel binary workbook files store information in binary format instead of the XML format like with most other Excel files. Since XLSB files are binary, they can be read from and written to much faster, making them extremely useful for very large spreadsheets. This also implies that with .xlsb files calculations will be faster and workbooks much smaller.
Advantage : Saving in binary allows formulas to be saved properly if they are longer than the 8192 character limit and macros, VBA code is fully supported.