It would help to know how the black line was created, and to see a screen shot of the table with nonprinting characters displayed (click the ¶ button on the ribbon).

At a guess, though, the cursor in the first picture is in one paragraph and the visible text and line are in a second paragraph. To bring them closer together, right-click in the first paragraph and click Paragraph in the menu; if the Space After is not zero, change it to zero. If it's already zero, then look at the Space Before setting for the second paragraph and make that zero.