Why you should keep resolution down when capturing
Screenium lets you capture in different capture modes. If you need the entire screen, go for Fullscreen capture but keep in mind that the higher your capture resolution, the harder your viewers will have to try and decipher which menus you open, which values you enter and which files you move. Best lower your screen's resolution first and capture Fullscreen then.
Most of the time, you'll have to get by with less than Full HD resolution with your finished tutorial. So the closer your resolution is to the resolution you'll export, the better. Another thing to keep in mind: always try to capture the same aspect ratio as the ratio you're going to export. And never capture below the target resolution.