Here's a few things to check: First, ensure you are displaying the top level ruler (in the View tab, ensure "Ruler" is checked in the Show group). Refer to the image below.
!Word menu display ruler checkbox(https://i.sstatic.net/0Aryt.jpg)
Next, with the top ruler displayed, verify that the right margin is not offset to the left. Go to Home tab, Paragraph group, then expand the paragraph settings menu. You can also type "Paragraph Settings" in the Tell Me box. Verify that the right paragraph is set at "0." Select the whole table and apply this so that the correct formatting is set for the whole table.
If the step above doesn't fix it, also go to "Table Properties" (type "Table Properties" in Tell Me box). Under the Table tab, go to "Options." In Options, you can set the left and right margins for the entire table. The default (assuming you've set the display as inches) is 0.08" but you can change it to something more or less.