Internal and external Conversions are made for SY-LANGU?

Hello Experts,

Please Find the attached images.

How Standard Function modules/Classes return Logon language as 'E' when used in Programs But as 'EN' when executed in se37/SE24 IN SAP ABAP.

Can anyone explain how the Internal and external Conversions are made for SY-LANGU?

PFA.

FM: RSCR_LOGON_LANGUAGE_GET

CLASS: CL_ABAP_SYST=>GET_LANGUAGE( ).

Thank You.