Index time field boost vs query result score

I was doing some tests with setting a field boost
{
"book":{
"properties":{
"content":{
"type":"string",
"boost":"3.0"
}
}
}

But noticed that the search result scores are lower with the boost applied than without the boost. I would expect the boosting factor to higher the overall score or is it unrelated.

Thanks,
Yannick