Thousands of Washington State Obamacare enrollees will be informed that the state’s health-care exchange underestimated how much they’d have to pay for insurance.

Approximately 8,000 Washingtonians are about to learn that for its first three weeks of operation, Washington Healthplanfinder, the state’s exchange, was erroneously sending their monthly incomes to the federal hub, which compiles data from various federal and state agencies to determine applicants’ eligibility for Medicaid and premium subsidies.