Effective PPI is the the actual PPI (the resolution at which the image was saved) divided by the scale factor. If you enlarge the image on the page, the effective resolution goes down, if you reduce it it goes up. I like to think about this like a printed balloon -- if you inflate the balloon the image gets larger by stretching just as the pixels get larger when you enlarge an image on your page.
as you can also see in the Link Info, the image is scaled to 143.3 %.
And that's the reason why your effective PPI is not matching the Actual PPI.
If your scale value was 100 % your effective PPI would be 300.
Effective PPI value is decscribing the value that will make it to an exported PDF (no downsampling set) or to print (not scaling the output, no downsampling).
There could also be two values in your Link Info for effective PPI if you habe stretched or squeezed your image. Then the x value will differ from the y value for effective PPI.
If both values are the same, InDesign is showing only one value (for x and y direction).