Welcome to the forum. It is often a shock to get such a diagnosis and will take a while to get your head around the numbers. It sounds like the 24.5 that was mentioned was from a spot finger prick test and was indeed high, however diagnosis is usually from an HbA1C test which would be done from a blood sample taken from your arm and sent to the lab. That test gives an average over the previous 3 months rather than a moment in time which can be influenced by all sorts of factors. A result over 47 mmol/mol would then be a diabetes diagnosis.
The level of between 5 and 7 mmol/l from a finger prick test is what people would be aiming at as a fasting or before meal level but would expect to have a 2 hour post meal reading of no more than 8.5mmol/l if their meal has been tolerated by their body.
It is when meals are too high in carbohydrates for the body to be able to cope with them because the insulin they are producing is not enough or cannot be used efficiently by the body so blood glucose levels increase to too high a level.
The way to deal with that situation is by reducing your intake of carbohydrates, some people will also need medication to help.
If you blood glucose was 24,5 from a finger prick test then you should probably have been advised to test for ketones with a urine dip stick.
What advice and follow up are you expecting to get.