URL-Parameter doesn't contain trailing zero

my router:

$router->add(
    "/Info-Base/Seite{page:[0-9]+}",
    [
        "controller" => 'infobase',
        "action"     => 'news'
    ]
);

URL: /Info-Base/Seite20/ getting in parameter only "2" - problem!

URL: /Info-Base/Seite23/ getting in parameter "23" - OK!

why this??