Look for line 35: $file_size = filesize($item_path);
Add the following on the line under it.
if ( $file_size < 0 ) $file_size = $file_size - $file_size - $file_size;
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Wrong file size displayed
Inside functions.php:
Look for line 35: $file_size = filesize($item_path);
Add the following on the line under it.
if ( $file_size < 0 ) $file_size = $file_size - $file_size - $file_size;