That has no effect. I tried switching it on (it's a bit different in the 2017 version, as it's in the Liquid Layout toolbox). All that happens is that I get a line across the text on every page. I adjusted the top margin down radically to demonstrate this, as shown below. The line through line 8 of the text is what I get. I made this adjustment on the Master Page -- and it does nothing.
Sigh. I figured it out. What I have to do is use the Selection tool and then click on the Master page but NOT, repeat NOT, within the text frame on the master page. This step is cleverly not mentioned in any of the tips or documentation that I looked at. When I click outside the text box on the Master page, the margins are adjusted.
In general, master text frames are not very useful and thus rarely used. As far as I can see your layout, You have to stay with the majority (you didn't need it).
btw, switched to CC2017 in the meantime, just to see the differences, and didn't find much:
Layout Adjustment is still in the Margins and Columns dialog...
However, it seems like You sorted it out, and that's fine.