If everything looks okay submit your files for review.
How to set createspace gutter.
Lastly set up the spine.
Page extent minimum inside margin inches minimum inside margin mm 24pp 150pp.
However traditionally gutter spines have also been the smallest of the margins since the recto and verso pages laid together each with a large gutter spine will create an unpleasingly blank look to the center of the book.
If you go to the margins tab of the page setup dialog and select bookfold or mirror margins from the multiple pages drop down and then try increasing the gutter and then the inside margin you will see what affect each one has.
Look at the back of paperback books for ideas and be careful to leave space for the barcode and trimming as per createspace instructions.
The gutter is in addition to the inside margin.
The gutter margins need to be sufficient so that the spine or the readers eyes are not strained while reading.
For createspace you need to use the following measurements.
You can go back and make changes if you need to.
These both mean the same thing so you only need to set one.
So if you want the inside margin to be 0 5 for all pages add this value in the gutter margin box and leave the inside margin field blank.
Review your project setup.
The minimum size of the gutter varies according to how many pages there are in your book.