Delivery Costs Entries(BEWTP = F/G/I/M) related to PO in EKBE

Hello..

I am new to MM and i have been checking the values of BEWTP field in EKBE.

I could see the following values related to Delivery Costs.

BEWTP = F / G / I / M

Can any one tell me what does each stands for and How can i get an entry in EKBE for each of the above type?

any help/input is really appreciated.

Thanks,

lt