What does 90 months in prison stayed for 30 years mean?

A sentence of 90 months in prison stayed for 30 years means that the prison term is effectively suspended for 30 years, during which the individual will not serve time unless they violate the terms of their probation or commit a new offense. If the individual complies with the conditions set by the court during this period, they may avoid serving the 90-month sentence altogether. Essentially, it's a form of deferred sentencing that allows for a chance at rehabilitation.