Start and end of slow-start phase

I have a good understanding of slow-start phase, namely how it only lets a few packets send at first, however this amount increments until the max is found in order to avoid congestion.

For the graph below however, how do I identify when the slow-start phase ends? I'm assuming it starts right in the begining at 0 seconds, which is when the connection would be established. I'm going to guess that the slow-start ends at 0.65 seconds? Which is when we only start seeing two dots (packets) on after another... Or rather would this just be because of congestion avoidance?