Exponential Retry Delay seems incorrect

Trying to achieve an exponential retry on NMVB of .5s, 1s, 2s, 4s, 4s...for a maximum of 30s.

The behaviour I observe is retries are performed after 0.5s, 0.5s, 0.5s....1s, 2s, 3.3s, 4s, 1.3s

Couchbase env built as follows:

    	CouchbaseEnvironment env = DefaultCouchbaseEnvironment.builder()

                .maxRequestLifetime(60000) // cancel, not reschedule after 6 seconds

                .kvTimeout(30000)

                .retryDelay(Delay.exponential(TimeUnit.MILLISECONDS, 4000 , 500)) // .5, 1, 2, 4, 4....

                .build();

See 2 attached files, retry behaviour that shows the time delta since previous packet and the source packet capture.

App behaviour is 2 perform a single 'set' operation against a vbucket which has been forced into replica state (to stimulate NMVB responses).