See http://es.zimagez.com/zimage/thunarbug.php
Moving to the correct product. Even after all this time, this bug is still valid. I'll contact the translation team for Spanish, let's wait them to fix this.
Fixed in 038fed474d9f214f03087408e5fecf842667ee7a and the next time the script will check the translatio status the acceleator will be moved from _B to _m.
Fixed by translators. Please report translation bugs always to the translation mailing list, or probably no one will look at and deal with them.