While selecting any slice in an android systrace, I see a value for self time. What does self time mean?
In addition to myselfmiqdad's answer, you can check out this talk from Android Dev Summit '19: https://youtu.be/v4kCRZ_O4Lc, which walks through the computation of self time, children time and total time in detail.
As for systrace, although it shows trace events instead of call stacks, they are organized in a tree similar to a call stack. So the concept for self time still applies: self_time = total_time - sum(children_total_time)