1-day view
Crediting an ad with a conversion within a day by someone who saw it but did not click.
They scrolled past. They did not tap. The next day they called you, and the ad is credited.
Why it matters for HVAC
This is where platform-attributed numbers and reality diverge most sharply, and it is switched on by default. Your existing customers see your ads. Your brand-aware neighbours see your ads. People who were always going to call you see your ads, and then they call you, and the report counts it.
That is not to say view-through credit is worthless. Demand generation works partly by being seen. It is to say a number containing view-through credit cannot be read as a number of customers the advertising created.
How it is measured
Reported separately when requested. The share of total conversions coming from view-through rather than click-through is one of the most revealing figures in an account, and one of the least often shown to the client.
A worked example
A month reports 48 conversions. Split out, 34 are click-through and 14 are view-through. A contractor told "48 leads from Meta" is being told something materially different from "34 people clicked and 14 more called after scrolling past".
These figures are invented to show the arithmetic. They describe no real business.
What to ask
Ask for the view-through share. An agency that has never separated it is reporting a blended figure it has not examined.
Where this is demonstrated
The Tracking and the Conversions API pillar scores every listed agency on what they document here, and gives you the questions that tell you which one you are being sold.