Confidence interval
The range a real result likely sits in. We always show the band, never a bare number that pretends to be exact.
A confidence interval is the honest version of a number. Instead of saying "you gained 12%", it says "you gained somewhere between 4% and 20%, and our best single guess is 12%". The band is the room for doubt that every measurement really has.
We show the band on every result on purpose. A bare point estimate looks more certain than the data can support, and looking certain when you are not is how SEO tools lose your trust. If the band is wide, the honest read is "we are not sure yet" - usually because the time window is short or the traffic is small.
Reading two bands: if the band for a change and the band for "no change" overlap a lot, the result is not yet distinguishable from noise. When the bands pull apart, the signal is real.
Worked example
A change shows +12% clicks with a band of +4% to +20%. Because the whole band is above 0, the gain is real. A second change shows +6% with a band of -3% to +15%: that band crosses 0, so we cannot yet call it a win - it needs more days of data.
Honest limits
A confidence interval assumes the future behaves like the window we measured. A Google algorithm update, a seasonal spike, or a tracking gap can move the true value outside the band. The band is a guide to certainty, not a guarantee.