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, if you haven't made your payment by the time the next due date comes, your payment is 30-days late and a notice will be placed on your credit report. Every 30 days a new late notice is placed on your credit report. The late notices progress in 30-day increments: 30 days late, 60 days late, 90 days late, etc. until you reach 180 days late. After 180 days, or six months, of non-payment your account will be charged off.