Windows 10 Full Screen Issue

So I open up Minecraft for the first time in a while, and notice that instead of a full window, I get a "little" window that came up. I didn't think it was a big deal until I maximized it and it didn't go into the normal full screen (without the header and taskbar showing all the time). This makes everything on the screen smaller and it's very annoying. I have included before and after photos. Please fix!