You are evidently using list-directed I/O (with a * format). When you use this, you give up control of where line breaks are inserted (among other things.)

If you have specific requirements on the layout, use an explicit format. You can use G format if you want the individual values displayed similarly to list-directed.

An alternative I don't recommend is to open the output file with a RECL= value that is the maximum line length you desire. This is non-portable.