The same. You are not looking for an absolute value but you are looking for a balance. The magic word is Syncronization.
The carbs should be adjusted so that they open by the same amount together (it is not always possible to get them identical but as near you can is good enough). How much they are open is really irrelevent (other than you set it up at tick over) but they do need to share the load equally. Once you have set it up for minimum engine speed then the level of suck should then be the same(ish) on all the carbs at all other engine speeds
There are tips and tricks in the Vulcan Verses. Reading them is a good idea.
If, like me, you use dial gauges then they are fitted with a small adjuster valve on each gauge. I adjust mine so that the needles on each dial are just twitching with the engine at about twice tickover and then slow the engine down for the actuall carb balancing bit. I have done mine and other peoples bikes/cars this way and never had a complaint after.
Mine is a Red one.
Colour matched Bungee straps