Page Layout View - Right Page Margin Too Big

Whilst working on a particular workbook, I came across something that I would appreciate some help with.

Essentially, when using the Page Layout View, the Right Margin is ~1.5 cm (0.4 in.) larger than what it's meant to be, regardless of if there are cells small enough to fit in the space.

As an example, below, I've set a document with Left and Right Margins of 0 cm, with a Cell Width of 0.58.

As seen below, the rightmost cell on the page finishes at around 19cm, rather than extending to (almost) the end of the page. What setting do I need to adjust to change the page cells to extend all the way to the end of the page?

Note: I don't believe it's a case of Print Margins, as the printer I'm using only has 3mm margins (as indicated by the coloured sections on the ruler.

Any insight is much appreciated.