Field help (CLCORD) 

The indicated value specifies the element calculation order. It allows the use of an other element previously calculated.

The element calculation order will be as follows:

SEEINFOThere is no coherence control on the assigned order. An element calculated on a tax incl. basis with an order lower than an element calculated on an ex-tax basis will be calculated after the latter in the order of the tax-incl invoicing element.