This is a technical problem that occurs only once per file during upload and no longer afterwards: the file is displayed with length 0 before transfer, because the hörbert software cannot determine the length of m4a files before conversion. In step 3, the file is still transferred. The next time the memory card is inserted, the correct duration is displayed in the playlist. Tip: If it is a very old.m4a file with copy protection (from the years 2003-2014), it cannot be transferred to hörbert. For this you have to download this file again without copy protection, Apple offers the "exchange" of these files: https://support.apple.com/en-us/HT201616