This summary is not the rule. The rule text controls.
If someone gets hurt or something goes wrong, and afterward the person or company responsible fixes the problem or makes changes to prevent it from happening again, that fix generally cannot be used as evidence in court to prove they were at fault the first time. For example, if a store owner adds a warning sign after a customer slips and falls, the new sign cannot be used to argue that the store was careless before the sign existed.
The idea behind this rule is to encourage people and businesses to make things safer without worrying that doing so will be used against them in a lawsuit. If companies feared that every safety improvement could be treated as an admission of guilt, they might avoid making things safer at all.
However, this evidence can still be used for other reasons. For example, if there is a dispute about who owned or controlled the property, or whether a safety fix was even possible, evidence of the later fix can be brought up. It can also be used to challenge someone's testimony if they say a certain safety measure was impossible, but records show they made that exact fix afterward.
