Справка LibreOffice 7.5
Converts double-byte (full-width) characters to single-byte (half-width) ASCII and katakana characters.
See https://wiki.documentfoundation.org/Calc/Features/JIS_and_ASC_functions for a conversion table.
Text: the text string that contains characters to be converted.
Applying the ASC function to a string composed of single-byte characters will return the input string without any modifications.
=ASC("LibreOffice") returns the string "LibreOffice". No modifications were made because all characters are single-byte characters.
=ASC("ライト") returns the string "ﾗｲﾄ", which is composed of single-byte characters.