Hard to see what he was saying without context of the actual conversation.
Might've been saying you'd be retained for 90 days for sure due to being very good, might've meant to be able to easily let you go it'd need to be before 90 days.
if ur not being kept they will most likely term you before 90 days, not after. if you stay past 90 they can't just term you, you have to go on corrective action. What position are you? why do you think you'll be termed? in my experience, the seasonal hires they keep on are ones who show up for shifts, work hard, and are willing to do whatever is asked. they usually make the best TMs