For the future please copy/paste text rather than screenshots where possible. Use the method described here when pasting it in.
The log was rotated at 11:12 so will have to look in the previous log file for the start of the boot. The previous one is called /var/log/syslog.1
Look for lines like
May 5 13:17:23 pi kernel: [00012.505925] .........
where the time in square brackets is the number of seconds since booting, so that line means that the kernel started up at 13:17:10. It takes a few seconds to get the point of starting the kernel so the power up will have been a few seconds before that.
