Marcy and Dalton have both answered your question. Just want to say the extra white space is the space left at the end of the capsule once you finish writing the text or if you right align a photo/ text/ amazon or ebay capsules or anything else then you will find white space either to the right or left depending on which side the text is less.
Nothing to worry about though it is not pleasing on the eyes. With practice you will come to terms with this problem.
BTW, the extra space between capsules is the white space you must have left in the preceding capsule.
It is always good to preview the hub before publishing to make sure there is no extra white space left.