First of all, it is pointed out that there should be spaces after English punctuation marks, which is the standard writing. As for why the interval is different, it is because your text is aligned at both ends, and the result of alignment at both ends is that the text must be close to the left and right margins of the page, so according to the number of lines of text, there will be sparse results. If you want to get rid of this result, you can adjust it to left alignment (only to the left edge of the page).