Every numerical threshold in the decision engine is a rule you can tune per account. The defaults follow Google's own recommendations.
The rules and their defaults
Smart Bidding threshold - 30 conversions before tCPA/tROAS is recommended.
Budget-lost IS scale threshold - 15% impression share lost to budget triggers a Scale recommendation.
Underperforming multiple - 2.0Ć target CPA flags a campaign for Review.
Scale increments (tiered by size) - 20% for campaigns under $100/day, 15% for $100-$500/day, 10% over $500/day. Bigger budgets move in smaller relative steps.
tCPA breathing room - 5% headroom above current CPA when first switching to tCPA, so the new target doesn't strangle the campaign on day one.
Hitting-target tolerance - Ā±15% band for counting as "on target".
Max cut per source - 30% cap on how much budget reallocation can take from any one campaign.
Learning period - 14 days for Smart Bidding to stabilise after a material change.
Rank-lost noise floor - rank-lost IS under 10% is hidden as normal variance.
Feeder tROAS premium - PMax tROAS must be at least 1.20Ć Shopping's (see The feeder strategy).
How to change them:
Open Rules for the account.
Adjust individual values, or apply a preset profile.
Save - and note that editing Target CPA or Monthly Budget here triggers an immediate re-analysis.
RELATED ARTICLES
Preset profiles - Conservative, Balanced, Aggressive
One-click postures instead of tuning ten sliders.
Account targets & budgets
The two numbers the whole engine is judged against.
The 4-level CPA baseline
How "hitting target" is decided - most specific signal wins.