The PC speaker is normally meant to reproduce a square wave via only 2 levels of output (the speaker is driven by only two voltage levels, typically 0 V and 5 V).
For example, if your payments for March and July 2010 were each one month late, the report may continue to show (for seven years from the date after each payment was due) that you were 30 days late twice in 2010, even though the tradeline for that account also shows your payments for the rest of 2010 were made on time.
However, the previous 30-day late payment will stay on your credit report for the credit reporting time limit, which is seven years. On the other hand, if you miss your next payment, a 60-day late payment will be added to your credit report, then 90, 120, 150, and 180 days late. At 180 days late your account will be defaulted or charged-off. You bring your account current again anytime before the charge-off.