If you want to show the calendar months in several rows, so then you can make this configuration.
For example, If you want to show months in 2 columns, maximum 2 months per row, so then you can make this customization:
Please open this file: ../wp-content/plugins/booking/css/client.css
at line 236
find this code:

.datepick-inline {
  margin-bottom: 10px;
}

and replace it to this:

.datepick-inline {
  margin-bottom: 10px;
  width: 575px ! important;
}

If you want to have other number of month rows, please change the width to other value.