When you open for binary, you read 1 ansi character at a time.
ASCII is 7-bit values, for a max of 128 characters.
ANSI is 8-bit values, for a max of 256 characters.
You almost never see true 7-bit ASCII anymore; you always see ANSI files which people just call ASCII as the first 128 characters are an identical match to the ASCII characters.
QB64 works with 8-bit characters (ANSI) and not any compressed 7-bit ASCII. All you ned to do is simply read a character and you’ll get the 8-bit value back for it.
Where you might be seeing issues is in the codepage your data was encoded in, causing the extended-ascii characters to not display properly, but that’s a different issue from your question completely.