The fuel/oil ratio required depends on the engine design, oil quality, severity of service, and how long you expect the engine to last. Always stay within the engine manufacturer's recommendations except, perhaps, if there has been a breakthrough in oil quality since the engine was made. That isn't very specific either.
In essence, there are some very expensive 2 stroke oils that are sold with the oil manufacturer's assertion that you can use very high fuel to oil ratios - perhaps 100 to one. Some of these oils may be capable of running higher ratios than "ordinary" 2 stroke oils. Some may not. Never go outside the engine manufacturer's recommendations.
Your Victa/Valvoline 2 stroke oil is a reputable brand and should be treated as an ordinary good quality oil. If you always run the engine in light to moderate service, you can probably go to somewhere nearer the 50 to one limit than the 25 to one limit. If you sometimes or always run the machine hard, stay close to the 25 to one limit. Just make a judgement on whether you impose severe, moderate or light service on the engine, and pick a spot within the manufacturer's recommended range.