I just opened a document I've been working on and did an ink coverage preview. For some reason it's showing all black colours as 75/68/67/90 even though I have the tex colour set to 0/0/0/100. It's also showing all the images to be over 240% ink coverage even though I modified them all in photoshop to be set to 237% ink coverage. Why is the ink coverage preview reading the wrong values for black in the document? Is this a bug or have I accidentally changed some setting to fix all black colours within the document to a certain value?
The Separation Preview would respond to a custom proof setup with Proof Colors turned on. So if the proof setup profile conflicted with the document's assigned CMYK profile you will see how 0|0|0|100 would get converted into the proof space in Sep Preview.
Native swatches and colors could also get converted if the document's CMYK Color Management Policy was set to Convert to Working Space when it was created. But in that case the actual swatch or color numbers would be changed and the default [Black] swatch is protected.
Placed CMYK images would get converted if they have an embedded profile that conflicts with the document's CMYK profile, so if they get converted to the default US SWOP profile you would expect a higher total ink limit because SWOP allows 300%. If you are trying to protect an image's CMYK numbers don't include a profile when you save it.