3.1 Assumptions (ii)
Note that, by convention, there is only one box in the matrix at the 'activities to outputs' level.
This shows all the assumptions that you need to make in order for the set of activities to lead to the set of outputs. This is to avoid having to write an assumption twice, if it applies to more than one activity.
Similarly the box at the 'outputs to purpose' level shows all the assumptions you need to make in order for the set of outputs to lead to the project purpose.