37mb Propane Gas Bottle Regulator With Built in Pressure Gauge Fits Calor Gas & Flogas with POL connection

Hello can I use this regelater on a big bottle for a static caravan red one thanks

Does this guage twll how much has is left in bottle or just pressure coming out

Is this suitable for a 47kg propane gas bottle

I had a new 13kg gas bottle delivered this week, but when connected, it only shows a 4 on the scale here, rather than 12. Any idea why that would be?