How To Fix TD133 - Styles beginning with 'Y' or 'Z' are reserved for customers

SAP Error Message - Details

• Message type: E = Error

• Message class: TD - SAPscript: Text editor, composer, forms, styles and fonts

• Message number: 133

• Message text: Styles beginning with 'Y' or 'Z' are reserved for customers

What causes this issue?

As a customer, you have tried to create a layout set whose name does
not begin with 'Y' or 'Z'.
As an SAP employee, you have tried to create a layout set whose name
begins with 'Y' or 'Z'.

System Response

The initial letters 'Y' and 'Z' are reserved for customers, all others
for SAP.

How to fix this error?

Select a name with a valid initial letter.

Error message extract from SAP system. Copyright SAP SE.