When using Advanced Bulb Ramping, you will want to change this setting to the maximum ISO you feel comfortable using in Bulb Ramping, but not higher than a maximum ISO supported by your camera. Most modern digital SLR cameras offer good image quality on default setting of 3200. With some professional grade cameras this value may be increased to 6400 or even higher.
Setting this value too high may lead to Promote Control being unable to continue with Advanced Bulb Ramping. Please consult your camera manual for the highest supported ISO setting.