You fly to Nice from wherever and the arrival time is 08.45. The plane will be ready for departure at 09.45 but due to minimum transfer time you should not depart earlier than 10.01 so your passengers can connect. Only 16 minutes idle time.
You should always give it a minute more to ensure you have at least 1 h 15 min. For example you could let all your planes arrive until 08.44 and the you can let them depart at 10.00.