Hi Desoki,
Array type field is not supporting by DMF framework. It is by design. if you want to import you have to customize in staging as well as target function.
you have to create three filed in staging as per array index.. and you have to mapped through generatesorting methods
exp:
staging.field1 = target.sorting[1];
staging.field2 = target.sorting[2];
...
...
hope it is clear to you.
Thanks
Bhaskar