What do numbers mean in rust bench information?

I benchmark my rust project with cargo bench and see information of result in console: I see many numbers... What it means?

2 tests
test bench_few_core ... bench:  26,249,920 ns/iter (+/- 2,836,381)
test bench_one_core ... bench:   6,087,923 ns/iter (+/- 752,064)

I thought there should be 2 numbers per test: math expectation (or mean) and standart deviation, isn't it?