Monthly parking is not pro-rated.
Most monthly parking is by calendar months only and they are not pro-rated. If you purchase mid-month you pay the same rate as you would on the 1st, and your time is not extended.
This is the same for subscriptions - they are never pro-rated or eligible for partial refunds.
Most long-term parking sessions or subscription can be cancelled within the first 3 days of a session start - however that is subject change and is not applicable at all locations.**