Hi Gaurav,
You can map the field PersonNumber to "Split By Value Changed" function, this in turn can be mapped to "Remove Context" function, which then should be mapped to "Collapse Context" function, and finally it being mapped to the target field "PersonNumber".
Explanation for the above : "Split By Value Changed" will split depending upon the change in value. "Remove Context" will group all those same values under one context. Finally, "Collapse Context" will choose the first element from each of those resulting context.
Regards,
Souvik