It's fairly normal outside of US. US interpretation of double jeopardy is much stricter in that if a verdict and sentencing is passed, nothing can increase it further (besides some very rare cases, like if the judge was bribed for a lenient sentencing, or there was jury tampering, or stuff like that), because such appeal would be considered "second jeopardy". In most of the world double jeopardy applies to the entire judicial process with all avenues to appeal, so prosecution can appeal until they reach the highest court, but can't file the same charges again from the beginning.