"Parking fine of £100"

I went to pick up my dad from Royal Free Hospital on 20:01:14 and has just received a fine of £100 for staying in the short stay car park. This was my 5th visit this month as my dad is seriously ill. I normally park in the main car park but this time my dad was waiting for me In the main reception on ground floor. As I got to the hospital I checked the board that stayed maximum stay 20 minutes, this was more than enough time for me to walk my dad to the car. When I went it dad's nurse announce me an unpleasant news and dad was emotional. I had to calm him down n get him a sweet drink to stop him from shaking and compose himself. I stayed in the car park for only 17 minutes. 3 minutes less than the restriction. If the restrictions had been amended it should have stated so clearly. I am disgusted and really shocked with this fine.