When the Trump campaign filed its latest campaign finance reports last weekend, the largest expense surprised a lot of reporters. Almost half of the money the campaign raised, $18 million, was spent on “digital and online advertising.” Specifically, it listed $8.4 million spent with Giles Parscale Inc., a web design firm whose portfolio included real estate firms, local businesses, a candidate running for Bexar County, Texas, tax collector — and the Trump family.

Before designing the Republican nominee’s campaign site, the small San Antonio vendor had previously worked for the Trumps designing Melania Trump’s site, as well as the site for Trump Winery. According to the San Antonio Business Journal, the firm had just 60 employees and was hired when Trump declared he would run for president.

As recently as June, the firm stated it would need to hire 100 employees to keep up with work on the campaign.

What does that digital work entail?

We know that the firm’s services include website design and website marketing. We also know that it has launched other sites like www.lyingcrookedhillary.com and published short video clips as well. But since candidates can lump consulting and digital ad placement on the same line, we don’t know how much was spent in either of these categories. Specifically, we don’t know how much actually went to design or to ad placement

WIth television ads, we can see the placements in Federal Communications Commission filings. We know when ads run, how many were purchased and how much they cost. But with digital ads, we don’t know very much at all. The Federal Election Commission has said the internet expenses only need to be reported if they are placed for a fee on another website. (We’ve previously written about how this internet blind spot could be troubling for disclosure.)

In terms of listing expenditures, some candidates itemize those digital ads while others hire an agency to place the ads for them so the expense appears as a single number paid to the agency creating and placing the ad.

Since internet advertisements are usually targeted to a specific demographic, only the people who are targeted by the ad will know it is out there. The only way to tell if campaigns are getting what they paid for in terms of this digital marketing is if those targeted people show up to the polls and vote.