If you want time bucketed on something other than the even increments, then you have to cheat a bit. Basically, you have to calculate an offset time, bin THAT, and then add back the offset. The following code assumes the data is non-sparse enough that there will be at least one event in the first 10 minute increment.
| addinfo
| eval MyBinField = _time - info_min_time
| bin MyBinField span=10m
| MyBinField = MyBinField+info_min_time
Sometimes when doing time binning, there is value in tossing in a fake start and end point before invoking the bin command.
| addinfo
| eval MyBinField = _time - info_min_time
| append [|makeresults | eval MyBinField=0 | eval FakeFlag="DeleteMe"]
| bin MyBinField span=10m
| where FakeFlag!="DeleteMe"
| MyBinField = MyBinField+info_min_time
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