[Appointments+] Appointment booking page has dates displayed incorrectly

Hi there,
The appointment booking front end has dates displayed in two rows.

E.g. for 19th Dec it is displaying as:
1
9
in a box. Please help to fix it.

The problem shows up when you view it on a mobile with smaller screen or reduce the width on a desktop

https://www.carmento.com/make-an-appointment/