Steps to reproduce:

1. Download and import attached project. (SimulationTime_Repro_803676.zip)
2. Open scene: main
3. Press play.
4. In hierarchy window, select "Interactive PS".
5. In inspector, change "Lifetime" of "New Behavior Script" component attached to particle system.

Expected result: In the same script, size on all axis should be equal to lifetime.
Actual result: Lifetime is always bigger 1-2 percent bigger.

Note: It seems that curves are late by several frames when simulating. If numbers are big, the difference can become even one second and more. Another particle shows that when it simulates naturally, the lifetime and the size from curve are always equal.

Note: The maximum size from curve (10), is never reached when simulating by script.

Reproduced on: 5.4.0b21, 5.3.5p1