Your first payment will be released on successful completion of onboarding including Proof of Life, Test Tx and agreement on your Statement of Milestones.
Milestones are paid 80% of their budget before completion (equally divided by Milestone length) and 20% upon completion. Final Milestone is 1-month long and is paid upon completion
Below can be found high level overviews of monthly batches calculation based on the length of each milestones.