lsmw - i can't change data in the recording , why ?

i add recording ( batch-input ) to my lsmw project ,

now i want to add line

xre3+0(3) = 'svg' .

now , if there was any value inside ( like 'aaabbbccc' ) ,

it was eraze and i see just : 'svg' .

but if i add line befor :

xref3 = '9999999'.

xre3+0(3) = 'svg' .

i see the result that i want : 'svg99999'

what can i do ?