Context vs Expression

Hi All,
I am using an embedded BPMN within another application.

If I use saleOrder?.saleOrderSeq under Context, it will work fine.

Once I change to expression, it does not return, though it it is the same line.

Any advise on wrapping the expression to context.

The reason is I need to add string like “Quotation Number” as a prefix to the expression.

Thanks,
Andrew