The usual reason for entering event scores is to make adjustments to the pair or teams outright score, usually to assign penalties or award some bonus such as the carried forward score from a previous event.
The pairs event scores entry screen is depicted above, and is very similar to the teams event equivalent. The teams event screen has additional fields as it contains both IMP scores and VP scores.
It is possible to enter directly the outright scores for the last and prior sessions or rounds, but that is an unlikely use for this screen. The prior and last session scores are updated each time a session is re-scored.