вот объяснение поведения, которое я наблюдаю:
Length of the screen field REFNR "SickCert. Number" is enlarged to 12 symbols;
The Number is stored physically in the same database field P2001-REFNR and the length of this database field is unchanged and equal 8;
New sickness certificates numbers(length >

are compressed to the 36-decimal number system (to reach the field lenght to be equal

automatically;
The database field P2001-FLAG4(Reserved Field/Unused Field) is used for indentification if the number is compressed(to 36-decimal number system) or not; if your solution already uses the field FLAG4 somehow - you need to copy screen 2033 into an own customer one 9xxx and set this screen as default for sicknesses data maintaining;
If some of your own reporting uses the P2001-REFNR as the sickness certificate number - you can use class-method CL_HRPADRU_UTIL=>NUM_36DEC_FROM in order to decompress(if P2001-FLAG4 is on) the number value. The class-method is provided with this Note;
If you enter a number which length is > 8 and the number is not numeric - this number cann't be compressed and will be cutted to length = 8 automatically without a warning. An appropriate notification will be added into infotype logic in the next Synchronisation HRSP.
Что печально.
А новых нот по-поводу поля ОГРН и кол-ва знаков в Номере б/л не нашел.
PS: оказалось, что номер б/л у нас в стране 12 знаков, так что просто взял Серию (15 знаков) и через CMOD поменял ее на ОГРН, а номер оставил как есть. Уффф !