@User: That's right. Drive strengths are "usually" given in numbers that represent drive strength in multiples of some base drive, but that should not be taken too literally. As such, "_0" does not mean zero drive strength, but probably half drive strength, or maybe just minimum transistor sizes on the output gates. Ultimately the gate resizer tool looks at the liberty file data and determines what cell is best based on the actual drive strength and not the suffix.