G/L class blank in purchase order

When I introducce a purchase order (non stock) in JDE for supplier 1 and ítem 1, when I press OK, the G/L class is blank in F4311 but in F43199 set the G/L class of ítem.

If I introducce an other purchase order (non stock) with supplier 2 and ítem 1, the G/L is not blank in F4311, it have the G/L class of ítem.

The suppliers 1 and 2 are iqual, it have the same values in F0101 and F0401.

The ítem is a non stock type.

Why does this happen?

Thanks you.

Elisa