Some of the spacing is from the table's cell margins. By default they are set to 0.2 cm. You can change those by right clicking on the table and selecting Table Properties then click Options on the Table tab of the dialog.

The rest of the spacing comes from the paragraph style applied to the text. If you don't want that then apply a more appropriate style such as No Spacing.

In addition, you should learn to use Word correctly. Formatting should be applied using styles, not directly applied by altering font size and applying attributes such as bold or italic.