It sounds like you have a installation of PHP which is without BC Math library.
This is problem only affects the Map of Orders in the Admin, it does not affect any other part of the program.
a. You can enable the BC Math library when installing PHP. Here is the official documentation: http://www.php.net/manual/en/ref.bc.php
b. Alternatively, you can remove the part of the code which requires the bcmod function. In admin/map_iframe.php, please remove the following code:
$hrs = floor(bcmod($sec,86400)/3600);
$mins = round(bcmod(bcmod($sec,86400),3600)/60);
The side-effect is that you will not be able to see the elapsed hours and minutes on the Map of Orders.