Pmp total time difference free time difference description and Calculation

Total floating time = LS-ES or LF-EF
The total floating time is for the same activity.
The free floating time is for two adjacent activities.
Free activity time = the earliest start time of the later activity-the latest end time of the previous activity
Total time difference = LS-ES for the same activity
LS: The latest start, ES: the earliest start

Eg: (the following columns are extracted from the Internet)
What is the formula for calculating the free time difference? There is an example of a known project that is about computing Free time difference. The earliest start time of the work is 9th days, the earliest start time of the work is 4th days, and the latest start time is 10th days, the working duration is three days. I know the total time difference = 10-4 = 6. Why is the free time two days? How can I get it?
 
The concept of free time difference can be defined by the single time difference in P130, or in another way, free time difference (free float)
It refers to the maneuver time that can be used in this work without affecting the earliest start time of the work after the tightening.
That is, for a job with a tight working schedule, the free time difference is equal to the earliest start time of all the work with a tight working schedule minus the earliest completion time of the job (earliest start time + duration) the minimum value of the income difference.
Take this question as an example: FFi = ESj-ESi-DUi = 9-4-3 = 2 days

Author: ygd266