Fuzzy behavior of FlowOps.delay

Question

I try to understand the method FlowOps.delayby experimenting with the code for two days, and there are some points that I obviously missed.

So, consider the following code:

val source = Source(1 to 100)
val flow = Flow[Int].delay(4 second, DelayOverflowStrategy.dropHead)
val sink = Sink.foreach(println)

source
  .via(flow)
  .to(sink)
  .run

I expected him to wait 4 seconds and then print las 16 numbers from the sequence (1 to 100). And he behaved accordingly and after 4 seconds he put off printed numbers from 85 to 100.

Now, if I change the overflow strategy to dropTail, it also behaves correctly and prints numbers from 1, ..., 15, 100.

That everything is fine.

Now comes the overflow strategy dropNewand the next one

val source = Source(1 to 100)
val flow = Flow[Int].delay(4 second, DelayOverflowStrategy.dropNew)
val sink = Sink.foreach(println)

source
  .via(flow)
  .to(sink)
  .run

, . 4 , 1,2. 4 3,4. 4 5,6. .

QUESTION1: dropNew ? 4 , 1 16, .

QUESTION2: backpressure, , dropNew. ? , 16 ( 16 - ), . , , 1, , , . , 4 .