The percentage of language strings translated means the proportion of the original Australian English language strings that are part of the Moodle core branch (eg, https://download.moodle.org/download.php/langpack/3.2/en.zip has 22955 strings in 3.3 MB).
All language packs that you may download from https://download.moodle.org/langpack/3.2/ contain only the translated strings; un-translated strings are hosted in AMOS.