Your example data table does not contain any columns named LSL or USL. Assuming they do exist, but are just missing from the display your code remains with a couple of problems. First, you are attempting to insert values into a list structure.
{LSL( : LSL ) , USL( : USL ), Target( : Target ), Show Limits( 1 )}
Because this is a list, it will not parse and evaluate itself.
The second item, is that, Spec Limits is a column property, and therefore, only 1 set of Spec Limits can be set for your column :Value. If you have a columns named :LSL, :Target and :USL, you will need to specify which row in the data table contains those limits. Below is one method that can be used to add the Spec Limits. In the code, I am assuming there are columns of :USL, :Target and :USL, and that row 5 contains the values you want to use.
Eval(
Substitute(
Expr(
:value << set property(
"spec limits",
{LSL( __LSL__ ), USL( __USL__ ), Target( __Target__ ), Show Limits( 1 )}
)
),
Expr( __LSL__ ), :LSL[5],
Expr( __USL__ ), :USL[5],
Expr( __Target__ ), :Target[5]
)
);
Jim