Minitab uses the terms "innermost" and "outermost" to indicate the relative position of the scales for multiple levels of groups displayed on a graph.
For a horizontal scale, outermost refers to the scale at the bottom of the graph, and innermost refers to the scale farthest from the bottom, closest to the horizontal axis.
Outermost is also sometimes referred to as Level 1. The scale directly above the Level 1 scale is the Level 2 scale, and so on.
For a vertical scale, outermost refers to the scale to the far left, and innermost refers to the scale closest to the vertical axis.
When you create a graph with grouping variables, the order that you enter the variables in the dialog box determines which variables are defined as innermost or outermost. Minitab uses the first variable that you enter as the outermost variable. The subsequent scale levels then follow the order of the variables.