percentage code is way off on large boards

[Boofo]

Can anyone plaese tell me what I am doing wrong in the following code that would cause larger boards with high post and thread counts to display these percentages really far off?

PHP Code:

$statscache['activepercent'] = vb_number_format(($numbermembers / $newuserid) * 100, 2) . '%';

$statscache['topthreadspercent'] = vb_number_format(($topstarter['count'] / $getthreadviews['count']) * 100, 2) . '%'; 


On my smaller board they are very accurate. But on a larger board they seem to be showing up like the following:

15,300 Posts (15,300.00%)

I have tried different variations of this and they all turn out the same.