cor-el said

The new tab page settings refers to the number of vertical rows where each row contains a variable number of icons (columns) depending upon the available space (window width), so do not confuse horizontal columns and vertical rows where each horizontal row consists of a number of icons.

I think this is different from how Americans use horizontal and vertical. We would always say a row is horizontal (across) and a column is vertical (down). At least, that's what I always way.