You downloaded the 32bit version of office probably. If you have Office 365 you can pick if you want 32bit or 64bit

I have Office 365, and indeed, 32 bit. At work it is also 32 bit. Maybe it's better this way, otherwise others won't be able to work with the database if it was created under 64 bit. Probably little use is made of 64 bit.
What is the advantage of this actually?

Ludwick
In theory, the 64 bit is faster. But unless you have an application, that is CPU intensive, you will not notice the difference.

Microsoft Access really doesn't take full advantage of 64-bit architecture but it's the way of the future so it's kind of something we've all had to deal with. I fought upgrading from 32 to 64 as well. You can read more about it here.