fix num640 class description

Signed-off-by: Christian Lüthold <biocodr@gmail.com>
corrected completely wrong JavaDoc

Signed-off-by: Christian Lüthold <biocodr@gmail.com>
changed JavaDoc to match the one of Number640

Signed-off-by: Christian Lüthold <biocodr@gmail.com>
changed JavaDoc to match the one of Number640

Signed-off-by: Christian Lüthold <biocodr@gmail.com>