SIZE / WIDTH

Automatic:
Text and Line elements will use the entire page width.
Object elements will have the same size ratio as on the Sense sheet, reflecting the grid in edit mode.

Percent of pagesize:
The width/height is set in percentage of the full page width/height.

Numeric values (page unit):
The width/height is set in specific values (default mm).
Unit can be changed in "Report Settings" – "Page" - "Unit"


Read the full article in the online documentation
Automatic (default) Percent of pagesize
Both elements set to width and height 50%