Gap smaller than the dividend
The ordinary state of trading after a record date: the price opens lower, but not by the full amount declared.
How to read the number
A buyer will receive the payment net of withheld tax, so the fair fall in price is measured by the after-tax amount rather than by the declared one.
When the metric lies
Withholding differs between holders, so no single correct size of the fall exists. A gap differing from the payment is neither a market error nor a signal.
Also known as: partial dividend gap