The report of the card (biṭāqah) describes many scrolls being weighed against a small card bearing the testimony of divine oneness; by Allah’s will the card outweighs them.
The example indicates that the final weight cannot be inferred from the ordinary physical size of the paper. The reality of tawḥīd may have a weight disproportionate to the apparent mass of a person’s faults.
It does not license abandoning obligations or treating sins as inconsequential. This specific report illustrates divine grace and the weight of sincere tawḥīd, not the cancellation of the rest of the Law.