Basically what the question says. I have 16 GB of memory and task manager says 8 GB are in use but it only takes up 3 GB compressed. Wouldn't I have 13 GB free even though task manager says only 8 GB are free?

Basically what the question says. I have 16 GB of memory and task manager says 8 GB are in use but it only takes up 3 GB compressed. Wouldn't I have 13 GB free even though task manager says only 8 GB are free?

Compressed doesn't mean "used". This new Windows 10 feature compresses data which would be paged out into the pagefile on disk in earlier Windows versions. But this causes disk IO and a delay when you need to read the data back.
If you hover over the first line of "memory composition" you see how much RAM was compressed and how many RAM is saved: