Differential backup schedule (BE 2012)

Hi,

- Refer to attached schedule (1401271659511c7621261a00de.jpg), am I need to change tapes on after Sat backup completed ??

- If I want to keep the schedule but want to change tape on every Mon, then the differntial reference must be Full backup of 3 weeks before ??

(140127103532b6e65fd6f524b5.jpg)

Thanks