Series are bets on sections of the wheel: Voisins (the big series around zero) — 9 chips, Tiers — 6, Orphelins — 5, 0-Spiel — 4.
«What the series plays for» is the value of one chip: the amount divided by the series' chips, rounded down to a multiple of 5. Voisins for 900 plays for 100.
On large amounts some positions of the series hit their maximum, and the rest is divided by fewer chips: Voisins 7, 0-Spiel 3, Orphelins 4 (Tiers stays at 6).