Ok, as others have said, it looks like a good boat, albeit a little overpriced, but given the state of the market at the moment ...
You may find the water capacity is in fact more. However it is enough but you may need to change how you go about using it. My wife and I manage on about 30 litres a day, and that is with two showers including her long hair washed every day, washing up and all the drinks needed. Keep a 20 litre poly Jerry or two somewhere out of the light as backup.
You may be paying a bit too much, but how much more would you spend if you continue looking, paying for more surveys etc?
If you can afford it, go for it - you could finish up with much worse.
P.S. Welcome to the wonderful world of boating!