This summary is not the rule. The rule text controls.
When a case involves huge amounts of paperwork, like thousands of pages of business records or hours of recordings, it's not practical to make everyone in court read or watch all of it. This rule allows a party to create a summary, chart, or calculation instead. This summary can be used as evidence to show what the full set of documents or recordings actually says, without forcing the judge and jury to sit through all of it.
But there's a catch. Before using a summary this way, the party who made it has to let the other side look at the original documents or recordings. They need to give the other side a fair chance, at a reasonable time and place, to examine the originals or make copies of them. This gives the other party a chance to check that the summary is accurate and fair.
The judge also has the power to order the original documents or recordings brought into court, even if a summary is being used. This gives the court a way to double check things if needed, and makes sure no one can hide behind a summary that might be misleading or incomplete.