1st charge fragments the place where the missile hits, the 2nd (larger) charge goes of 100ths of a second later after the missile has moved through the fragmenting damage.
The time interval can be set prior to launch based on the outer material of the target.
Superb for demolishing buildings and fortifications.
Not so sure about bridges. First charge would probably take it through the deck. 2nd charge would thus probably not be as effective than against buildings and fortifications as it would detonate in the air under the bridge.
If accurate enough to hit a pillar thiugh, it could be devastating.