How should filling consistency across multiple heads be verified on a commercial liquid filler?

Number each filling head and verify its individual average and deviation instead of trusting the combined average. For multi-product use, run representative low, medium and high operating points to expose the available adjustment range. Where several specifications apply, document each setting so future operators can reproduce the approved process. Reject any unspecified maximum-capacity claim when your real application demands a defined quality level. This also lets you estimate utilities, staffing, spare parts and expected maintenance before the filler is installed.