Earlier quoted context omitted.
It's a way to represent that value. The number does not itself store the value, nor does changing the number transfer the value. It's true that people work hard for that representation, because we've built systems where the link between the representation and the underlying value is quite strong, but it is still just a number at the end of the day.
That number that you don’t think is real lets you claim actual resources now and in the future. I think you should equally be confused about abstractions such as university credentials, or citizenship.
And yes, those others are great examples of this principle. The diploma is just a piece of paper and an entry in the university's records. Set it on fire and I still have all the skills and knowledge. Give me a good solid blow to the head which breaks the skills and knowledge, and you've destroyed what's actually useful and interesting, even though the diploma is completely intact. Likewise, citizenship is only relevant because it convinces other people to let me do things like work, cross borders, and vote (which is a whole other number-that-does-stuff-because-people-happen-to-agree-on-it system).
I'm not confused and I don't think money isn't real. I just understand what it actually is, versus what people agree to do with it. It's a typical example of the map not being the territory. Money exists, but it is not wealth or value. Money in an account is a number. Money as a system is a collective arrangement where money can be exchanged for goods and services, usually.