The 'Sequence' field in the 'User Workload' entity field is used for deciding the sequence of the users. This Sequence field is a numeric field and starts with 0.
Only Lead Assignment Administrator or System Administrator can change the sequence of the user. An administrator can directly change the sequence from the sub-grid and would not need to open each record to change the sequence.
The records will get assigned from lowest to highest sequence and will work with both Round Robin and Capacity algorithm.
By default all users will have 0 sequence. If no sequence is provided then the records will get assigned by date when the user workload is created (i.e. date when a user added in the queue).
You cannot add duplicate sequence number for two or more users. It will restrict the user from adding same sequence number for the users.