The Sequence Settings dialog allows you to specify settings for animation rendering. This dialog is only accessible from the Render Animation dialog when Output File(s) is set to Image Sequence.
First frame number – Specifies the animation frame to start rendering from.
Skip existing frames – When enabled, Filter Forge will check if any output images for the sequence already exist in the output path before rendering. This allows you to cancel rendering mid-way and resume it later without having to re-render frames that have been completed previously.