You will likely get better program help in a program forum
The Cloud forum is not about using individual programs
The Cloud forum is about the Cloud as a delivery & install process
If you will start at the Forums Index https://forums.adobe.com/welcome
You will be able to select a forum for the specific Adobe product(s) you use
Click the "down arrow" symbol on the right (where it says All communities) to open the drop down list and scroll
Reply with the program name and I will move this message
Sorry, can you move it the Question to the InDesign forum?
Change the size(s) of the master page(s) of the alternative layout. Use the page tool to do it.
That did it!! Thanks Willi