What do those insurance codes mean?

2           Coinsurance Amount
3           Co-payment Amount 
23         The impact of prior payer(s) adjudication including payments and/or adjustments. (Use only with Group Code OA)
27         Expenses incurred after coverage terminated
45         Charge exceeds fee schedule/maximum allowable or contracted/legislated fee arrangement
222       Exceeds the contracted maximum number of hours/days/units by this provider for this period.
226       Information requested from the Billing/Rendering Provider was not provided or not provided timely or was insufficient/incomplete.

CO        Contractual Obligation 

OA        Other Adjustment 

N10       Adjustment based on the findings of a review organization/professional consult/manual adjudication/medical advisor/dental advisor/peer review. 
N517     Resubmit a new claim with the requested information.
N640     Exceeds number/frequency approved/allowed within time period.  
N650     This policy was not in effect for this date of loss. No coverage is available.

PR        Patient Responsibility