onload time in F12 XML output

Looking at the XML file captured via F12's network tab, I am not able to correlate onload time with any URL. How can i see which page this is for? 

For example, which URL took 8116 ms to load:

<pages>
<page>
<startedDateTime>2015-09-18T21:10:52.822-08:00</startedDateTime>
<id>0</id>
<title/>
<pageTimings>
<onContentLoad>8113</onContentLoad>
<onLoad>8116</onLoad>
</pageTimings>
</page>
<page>
<startedDateTime>2015-09-18T21:11:36.970-08:00</startedDateTime>
<id>0</id>
<title/>
<pageTimings>
<onContentLoad>-1</onContentLoad>
<onLoad>-1</onLoad>
</pageTimings>
</page>
<page>
<startedDateTime>2015-09-18T21:12:15.424-08:00</startedDateTime>
<id>1</id>
<title/>
<pageTimings>
<onContentLoad>-1</onContentLoad>
<onLoad>-1</onLoad>
</pageTimings>
</page>

Also when I test with one page, sometimes onload time is not accurate if i see all the object load time in Fiddler. Are there any open bugs around it? Is there any explanation how this onload time is calculated?