If your net monthly pay is $5000, here is how you would find your 20/10 numbers:

Multiply your net monthly pay by 10% 
$5,000 per month x 0.10= $500 
Then your annual pay by 20% 
($5,000 per month x 12 months) x 0.20= $12,000

Therefore, your overall consumer debt should not exceed 12,000
and your monthly debt repayment should exceed $500