Doubt on table PMCO (Plan Maintenance Cost)

Hi all,

i have a doubt about DB table PMCO (Plan Maintenance Cost).

There is a key field called GJAHR to display data yearly,but i need to calculate costs monthly....How can i do it? Can i use field from WRT00 to WRT16?

What do these fields (WRT*) represent?

Thanks in advance.

Regards.

Dario.