As stated in your owners manual, that is the "change oil" reminder indicator. The change oil reminder should be reset each time the oil is changed. Again, the instructions on how to do so are included in your owners manual.
RepairPal Certified shops can diagnose and repair your 2007 Chevrolet Trailblazer. They provide transparent pricing with a minimum 12-month or 12,000-mile warranty on repairs and services.