About SAVEFILE

Hey guys! I have a question about my savefile. i see in game editor my dates prestige:

Example:

"key": 1,
"data": {
"bloodWebLevel": 50,
"prestigeLevel": 3,
"prestigeDates": [
"2018-01-12T08:40:10.392Z",
"2018-02-20T13:18:17.974Z",
"2018-03-10T21:31:33.783Z"
],

What does mean: 392Z", ?
Can i remove these?! make any sense?! Help please. Thanks.

Don't remove them it's mili seconds or idk but are important

okay tahnks