Is it sad that I know EXACTLY what's going on here even without a translation?
(Even though you can't do this in-game)

it's quite possible, arash has self charge NP 3rd skill so he can blow himself up the first round so helena can jump in and give everyone else 20%. but that needs to be lvl10 to work

To be fair, any Servant skill with a NP charge or self-charge is something you want to max if you are using the Servant in question. Or at least get it high enough to fill 20% of the gauge.