I need to create a code for labels: an individual label with a GS1 Data Matrix code and a summary label with a barcode. My code looks like this

(01)40453958013406(3103)001000(15)290226(10)260927

The client said that the GTIN code is too short and that I should add a 0 at the beginning so that it looks like this: (01)040453958013406(3103)001000(15)290226(10)260927

But when I add a zero in the program, the rest of it—that is, (3103)/(15)/(10)—stops working and some other numbers appear. Could someone help me fix this?