Anchor double calendar

Anchor double calendar

When I put a bottom anchor on my calendar control, it doubles the calendar
and shows two months.
All I want is for the calendar to stay at the bottom of the panel when the
form gets maximized.
Before anchor :

After anchor :

Is this normal ?
If it is, how can I make the calendar stick to the bottom of the panel
without an anchor ? because the anchor works fine with every other
controls I have.