Layoff notice, what does the 60 days mean? after 18 years as a teaching assistant

Our team was told about a closure date that is 16 weeks away. I have read a lot of threads here and could not find my exact situation. I do not know if I should start looking now or wait for severance news. Should I stay for the bonus?

Write down key dates and keep copies of the notice. Mine helped when a question came up later.