Question about iControl response for get_performance_graph_csv_statistics

When I query for the performance data, I query for the previous minute. I get the current time and retrieve the completed minute from the time. Also when I checked the rrd database and I see the data getting collected for 10 secs duration and then grouped into 60 secs buckets e.t.c. Does RRD database normalize all the previously stored data every time? For testing purposes I waiting for 10 secs after expiration of a minute and tried the same test. I do see the same results.