From Nasdaq: 1st is Deficiency notice, then if company still does not meet listing requirements by end of the 180 days, a Determination Letter will be sent. The company has 7 calendar days after receipt of the determination letter to appeal the delisting. If the company can show a meaningful plan to deal with the non-compliance issue, it will generally be granted another 180 day extension to do so.
"Determination Letter. If the company is not in compliance within the time period prescribed in the deficiency notice, Nasdaq sends a "determination letter" informing the company that Nasdaq has determined that the company does not meet the standards for continued listing. The company then has seven days to appeal the determination. Under Nasdaq rules, the company must publicly announce within seven calendar days that it has received a determination letter and the basis for the delisting."