In the classic Step & Repeat Tabular ticket you can use S&R specific SmartNames as, for instance, for the total width of the S&R's sheet and plate. These are automatically calculated based on the stations size, the vertical and horizontal count, space between stations if any, etc.
Such SmartNames are not available in a ticket of the task "Step & Repeat Tabular (Dynamic)".
In a Step & Repeat Tabular (Dynamic) task, if you need such calculations for the Sheet and Plate values, you have to create four Script SmartNames: one for the S&R Sheet width, one for S&R Sheet height, one for the S&R Plate width and another one for S&R Plate height. These are typically simple calculations.
For example: When your already have a SmartName for the 'horizontal count', then your Script SmartName for the S&R Sheet total width should just multiply the Page Width by your 'horizontal count' SmartName:
And then use this SmartName in the horizontal Sheet Size field of the Step & Repeat Tabular (Dynamic) ticket: