Payment Module

Hi all!

In a Danish database (3.70) I found an (AddOn?) module for Payments (Version List PM3.01.01.2.02).
In table 6016818 Payment Ledger Entry there is a field named UPR-No. which is filled OnInsert of a record by calling this function:

AssignUPRNo() UPR : Integer
// AssignUPRNo

PmtSetup.GET;
PmtSetup.TESTFIELD("UPR-No. (Min.)");
PmtSetup.TESTFIELD("UPR-No. (Max.)");
RANDOMIZE;

UPR := RANDOM(PmtSetup."UPR-No. (Max.)"-PmtSetup."UPR-No. (Min.)"+1)+PmtSetup."UPR-No. (Min.)"-1;

PmtLedgEntry2.SETCURRENTKEY("UPR-No.");
PmtLedgEntry2.LOCKTABLE;
IF PmtLedgEntry2.FIND('-') THEN;
Attempt := 1;

REPEAT
  PmtLedgEntry2.SETRANGE("UPR-No.",UPR);
  Ok := NOT PmtLedgEntry2.FIND('+');
  IF NOT Ok THEN BEGIN
    UPR := RANDOM(PmtSetup."UPR-No. (Max.)"-PmtSetup."UPR-No. (Min.)"+1)+PmtSetup."UPR-No. (Min.)"-1;
    Attempt := Attempt + 1;
  END;
UNTIL Ok OR (Attempt = 100);

IF NOT Ok THEN
  ERROR(
    Text000,
    PmtSetup."UPR-No. (Min.)",
    PmtSetup."UPR-No. (Max.)",
    PmtSetup.FIELDCAPTION("UPR-No. (Min.)"),
    PmtSetup.FIELDCAPTION("UPR-No. (Max.)"),
    PmtSetup.TABLECAPTION);

What is a UPR-No, what is it used for? Why is it created randomly? Could it be skipped/ignored?

Please enlighten me!

Kind regards,