Do you have resources allocated against the task(s)? If so you may find
that the resource work is less than the duration of the task. The dots then
show that portion of the activity duration that exceeds the work of the
resource allocated to the task. If you do have a resource allocated to the
task, then depending on what the task type is, will depend on how to 'fix'
the dots. As an example, if you have fixed duration for the task, then set
the units to 1 and the work to be equal to that of the duration. If the
resource is only going to be allocated for a percentage of the duration, then
having fixed things, set the percent allocation to the value you need.
Hope this helps