Code 39 barcode is much longer than it should be, typically as wide as the page

When you position horizontally the cursor using blanks to put the barcode at the right place, you must send the barcode selection sequence after sending the space characters to move horizontally. If you do not do that, the spaces are part of the barcode data and the barcode is much wider than expected (usually across the page).

If you can only send the barcode selection sequence at the beginning of the line, use the special 39 symbology with no starting spaces (IDs 24670 and 24671).
This symbology will not include the starting spaces in the barcode data.