Hey Jason,
first of all, thank you for the purchase and my apologies for the slow reply!
The margins on both sides of the content in Ikebana are intended behaviour – since the width of the masonry blocks is fixed, it is impossible to adapt to all screen sizes without either allowing the content to not fit a whole number of tiles (which would be ugly) or changing the margins around the content; in other words, Ikebana’s content width algorithm works in steps – when the width of the screen decreases, the content always accommodates a whole number of tiles by width. The screenshot from your table is exactly the case just after such “step” has been made – the content width shrinks to accommodate less tiles (3 instead of 4), so the margins increase; if you reduce the width of the content further, the margins will become smaller. On mobile phones (screens below 732px in width) the margins are narrow all the time. You can try resizing the website in your browser all the way down to the minimum width to get a feel of it :)
Please let me know if I misunderstood the question – or if the explanation wasn’t clear enough (I can imagine the latter).
Sincerely,
Andrii / Satori Studio