Field help (UTIFCYDEB) 

Only the account postings entered in the sites where the code is greater than or equal to this start range will be selected.
If this field is empty, there is no control.
The site must belong to the company to which the bank is attached.
If a site is defined in the bank record, then the entry of the site range is prohibited. Only the account postings entered in the site for the bank will be selected.

NB : The selection of the account postings is simple and concerns only the postings passed to the company for the bank.