Use at least two loop blocks when selecting

What causes this issue?

You are defining or maintaining a step loop and have chosen <LS>Sel.
loop block end</>.
You must define the position and size of the loop block as a
rectangular screen area. One corner of the loop block was already fixed
and the opposing corner is determined by the cursor position.
In most cases, you define loop blocks as one-line loop blocks, but the
rectangular area is a special case since it is part of a line.
The system first attempts to create a minimal step loop from two loop
block repetitions. However, there is not enough free space for this
below the defined loop block.

System Response

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

How to fix this error?

Place the cursor so that you define a loop block which has space for
two repetitions and repeat the function.

Error message extract from SAP system. Copyright SAP SE.