I checked the size of the file itself - it said it's 4.02 GB. I checked the size mentioned in properties of the database using SSMSE - it said the size was somewhere above 4000 MB.
I then executed sp_spaceused and it said that the file size was above 4500 MB and the unallocated space was close to 4100 MB.
I'm a little confused as to how this works. I'm using SQL Server Express so I need to monitor the db size to figure out if it's reaching its limit. How do I figure out the in-use db size?