Rect Transform strange for different Device Sizes

Hi, please check the image to better understand my issue.

I once made a project, which worked for both ipad and iphone sizes (Project 1). In that project I have a rectangle which has the same absolute size.

Now I have a new project (Project 2 in the image), where I need to make almost the same rectangle box. But this time handling different sizes doesn't work. The first weird part is, that I need higher values for width & height than in the previous project. It seems like I somewhere picked another resolution, but I don't know how and where. But the complicated part is, that switching between Iphone and Ipad makes the rectangle smaller/bigger. If I optimize the size height for IPhone, then it doesn't fit the IPad and vice versa.

What is the problem?