Field help (SIPAMTDIF) 

If the option 'Recover the postings on the first currency found' has been selected, all the recorded postings in another currency will be converted by using the rate defined on the first posting associated with the 'first currency found'. This conversation can lead to a rounding variance to balance the document in currency.

This field is used to define a maximum authorized rounding variance. If this variance has exceeded, an additional option is used to recover the postings in local currency or to scatter the rounding variance on the postings of the X3 document created.