Tenant giving notice but not according to contract

[Jeff Marburger]

I am new to being a landlord, just 7 months now.  I have a one duplex unit.  The renter upstairs came with the duplex when I purchased it.  The renter downstairs I found.  There is a month to month contract that requires that the tenant or landlord give notice in order to terminate the lease it says "This lease will continue in full force and effect on a month to month basis unless Tenant or Landlord provide a written notice to the other party at least 30 days before the end of the current month in order to terminate the lease."

I thought this meant if I am not notified by the 1st of the month then the tenant plans to stay the following month and pay rent the first of that month.

So my downstairs tenant sends me a notice on the 9th of November saying she will be out by December 1st.  Do I forget it and move on?  Or tell her this is not proper notice?