First let me mention, that the current animation time is being measured in ticks - 4800 ticks per second. Depending on your frame rate you'll get the corresponding value for one frame (when using the default rate 30 FPS, one frame corresponds to 4800/30 = 160 ticks).
Please describe more in detail, how the final effect should behave.
For example, to move it on the Z axis you can use the following expression:
fpItem.position.z = min(Max.time/160, 0);
Thanks in advance for any further comments.