I'm quite sure you can't use a calculated field in the pivot table to isolate those with the entire mattter greater than 250. You can however add a new column to your source table to return a true of false if the matter is greater than 250.
Referring to your table, if it were to begin in A then the next available column would be A, so you could use this in A2.
=SUMPRODUCT(--($A$2:$A$9=$A2),--($B$2:$B$9=$B2),$D$2:$D$9)>=250
Give the column a title and then include it in the page segment of your pivot table and set it to show TRUE only.
Also did you know you can place a filter in the Total column in the pivot table (not many people do). Select the cell to the right of 'Total' > shift left arrow to select it and the 'Total' field > hold shift and go down to end of range. Then turn on autofilter and filter custom by everything greater than or equal to 250.