"But whenever I adjust the left margin and the scale, It jumps to another page."
Had you noticed how small the right margin is, compared to the left margin in my example?
Left margin controls the position of the left side of the table.
Right margin triggers when the last column will jump to the right (and onto the next page in that direction).
My two goals when setting the margins (and the scale) are to leave enough room on the right side to keep the table on one page, then adjust the left margin to push the table to the visual horizontal centre of the page. The five settings (scale, and four margins) shown in the right sidebar gave the result I was looking for.
Regards,
Barry