Medical Cert

Hi,

Just curious on medical certificates required by my employer. I had recently had Monday and Tuesday off sick, called in sick an hour before my shift started Monday. When I called in again on Tuesday I was told by my boss that I would need a med cert, as Sunday (which is one of my normal days off) counts as part of the 3 calendar days as per my contract. Looking at the snippet from the employment nz website (attached photos are of the employment nz website and the part of my contract) I would think that Monday would’ve been day 1 and as they have asked for a med cert then they will have to pay me back? Or does sunday count as day 1? Thanks in advance