If a third party paid your lost wages and medical expenses (your employer, for example) In some situations, if you get an insurance settlement, you have to reimburse these people out of the settlement you get.
I don't know if the above is the law or not, but I know someone who was in a similar situation and had to pay back her lost wages because the during the time she missed work, her employer paid her salary.
This could be a similar situation to yours', and the insurance company is holding back a certain amount to pay your employer back, and to pay your medical expenses, if your own insurance company paid for your treatment.
I don't know any of this to be a fact, but it could be an explanation.
