How to use timechart to show increase in recent 7 days

[bestSplunker]

hey, I cant use |timechart count span=1d to calculate recent 8 days count, search result as follow:

_time           count
2020/05/21       100
2020/05/22       120
2020/05/23       180
2020/05/24       200
2020/05/25       270
2020/05/26       380
2020/05/27       490
2020/05/28       680

now,I want to calculate the increase quantity of each day compared with the previous day. The results should be as follows

    _time           increase 

    2020/05/22       20
    2020/05/23       60
    2020/05/24       20
    2020/05/25       70
    2020/05/26       110
    2020/05/27       110
    2020/05/28       190

then use timechart show the increase quantity |timechart count span=1d

is there have a simple search statement to do it?

[to4kawa]

|timechart count span=1d
| delta count as increase
| table _time increase

use delta