Select end of area

What causes this issue?

When you create a subscreen area, define the size of the area after
assigning an area name. To do this, select the bottom right corner of
the area.

How to fix this error?

Define the size of the area so that it is sufficiently large to
accommodate the subscreen. Starting at the top left corner of the area,
select the right and bottom of the area so that no fields in the screen
are concealed. On the right and the left, there must be at least one
blank space between the area and the fields outside it.

Error message extract from SAP system. Copyright SAP SE.