I got it
Find this part in the functions.php and the function get_categories
$count++;
$count2++;
$categories .= "</td>\n";
After this add
if($count == 2) break;
The number is how many cats will appear on the home.
There are two probs in this case... it works, BUT
1. not only on home, also IN the categories it will cut the subcategories
2. Only 2, 4, 6 etc. are possible (no even counts)