This is the test code:

    qInfo() << QString("%0456%01%02%03").arg("a").arg("b").arg("c").arg("d");
    qInfo() << QString("%0456%01%02%03").arg("a", "b", "c", "d");
    qInfo() << QString("%04567%01%02%03").arg("a", "b", "c", "d");

This is the test result:

"d56abc"
"dabc"
QString::arg: 1 argument(s) missing in %04567%01%02%03
"%04567abc"

"d56abc" <- this is correct!
"dabc" <- in muti-arg mode, % eats 2 more numbers (56).
QString::arg: 1 argument(s) missing in %04567%01%02%03
"%04567abc" <- throw an error, when numbers longer than 4.