@Lisa75
What you want is not possible, because there is an "if-then" situation here. If the guest books minimal 4 weeks for 1th of november, then there is 50% discount in first week and 30% discount in next weeks.
There are several ways to set a discounted price: set a fixed price for month november, use rule sets (most flexible, but professional tools needed) to apply discounts to certain time periods, or manually code the discounted prices right into the november calender (then there is nothing averaged). But in all situations you at least need to set the min.stay to 4 weeks (when using rulesets you can do this for stay starting in first week only)
best regards,
Emiel