Debugging WordPress database show different info

Im trying to analyze queries of WordPress database of my website to look if there are speed lags performances.

I both used the php functions

<?php echo get_num_queries(); ?> queries in <?php timer_stop(1); ?> seconds

and it returns me this: 55 queries in 1,149 seconds

then i also analyzed the queries with a plugin: Debug Queries

in this case it returns me this:

Total query time: 0,19168s for 56 queries.
Page generated in 1,00000s, 80,83% PHP, 19,17% MySQL

I want understand why there are so different result in terms of query analyzed, 55 first case and 56 in second, and so different time 1.149secs and the other 0.19168secs.

Thanks a lot.

P.S: i optimized database before.