My understanding is that it means no sin is a barrier to heaven as long as there is true repentance.
Otherwise some sins would condemn a person to Hell for eternity. It all gets a bit complicated: which sins are deserving of an eternity of punishment? What about context? Can you cancel out sins with good deeds?
Which is why for centuries Catholics had the concept of purgatory, which doesn't have a biblical origin and the Vatican removed it from Catholic dogma some years ago.
Of course, the concept of Hell Christians have had since medieval times also doesn't have a biblical basis, which throws a different light on the concept of dying for our sins.
Theological interpretations are immense, varied and complicated - there's been 2000 years of people trying to apply simple messages to all sorts of different situations and the powerful throughout history have used them for their own ends, too.
To those taking the opportunity to deride Christianity...My own view is that it doesn't really matter if God exists, if Jesus was his son who performed miracles, died for our sins and rose from the dead...
Historians are fairly unanimous that a man called Jesus once existed, lived in the middle East, was a religious teacher who preached a simple message: be kind to each other, share - don't hoard - resources.
The world would undoubtedly be a better place if we managed this.