I am a newbie to testing. I have tested 5 times now within 2 weeks. Can you help me determine when the "black dot" is gone for the CYA test? The tube on the left is 50 CYA. The tube on the right is 45 CYA. 50 CYA tube has a faint trace of black dot. Am I being too anal about this? Which CYA level do the experienced folks think I have in that tube?