about boiler hydrometer?

I have a central heating boiler sr.no.0229L81794. The question is about the hydrometer. The hydrometer indicator is used to be on 1, now suddenly the indicator is on 4. is there any problem the pressure showing 4. when the pressure go down from 1, it used to open the valve and maintain the pressure 1. now the indicator on 4, eventhough boiler working ok. what to do to maintain the pressure from 4 to 1? is there aany problem if the indicator remain on 4?