Time to get nerdy
It has to do with a few factors:
1) how the original file was made
2) what program you’re using to open it
3) what your specific color management settings are in your Adobe suite.
Corel (like Illustrator) is a vector based program. Photoshop is a raster based program. The two are fundamentally and completely different in how they handle image data - including how they interpret color.
Photoshop is MUCH more powerful in terms of color management. The way that Photoshop is set up by default (unless you've changed your advanced color management settings) is to take whatever file you open and not only rasterize it, but convert it to a specific color space. Meaning even if you have vector image you made in Corel with a pure black (100% of only K), Photoshop will most likely display that black as a combination similar to what you are seeing (a "build", or "rich black"). It can be even more confusing because depending on your output settings, these numbers will be different after you save the file.
Illustrator (and probably Corel) don't do nearly the same amount of color management, especially if you're just placing the file as opposed to opening the original. You will never get an accurate color reading using the eye dropper tool on a placed image in Illustrator because technically it's not sampling the file itself - it's sampling a preview of the original file. Placing a file inside another document is like making a shortcut on your desktop - it's only an alias, or a link to the original location.
Like ColorCrest mentioned, it almost doesn't matter because your RIP is going to change these color builds, so after you finish reading my dissertation you can probably just chose to not worry about all of this unless you're experiencing a specific color problem.
Feel free to dm me, I went to school for way to long studying this stuff and would be happy to make all those years (and debt) useful to somebody