Comcast's February announcement of a planned $45.2 billion acquisition of Time Warner Cable came with the promise to divest itself of 3 million subscribers, a move to appease regulators who might be wary of the country's two biggest cable companies joining forces.

The details weren't revealed at the time, but today Comcast said that 1.4 million TWC subscribers will be transferred to Charter in exchange for $7.3 billion cash if the merger is approved. Additionally, Comcast will spin out a new "publicly traded company that will operate systems serving approximately 2.5 million existing Comcast customers."

That adds up to a net reduction of 3.9 million video customers from the merged Comcast/Time Warner Cable entity. Comcast had 21.7 million video subscribers at the end of 2013, while Time Warner had 11.4 million. Charter is the fourth biggest cable company (after Cox) with 4.3 million customers. Charter could become the second biggest, with Cox remaining at third, after the Comcast/TWC merger and divestitures.

After divestitures, the combined Comcast and Time Warner Cable would control a bit less than 30 percent of the country's multi-channel video programming market. The Federal Communications Commission formerly issued a rule limiting any one cable provider to no more than 30 percent of the overall video market. That rule was thrown out in court, but Comcast is still trying to stay under 30 percent to make regulatory approval more likely.

Comcast and Charter also said they would trade 1.6 million customers after the merger. This won't affect the total number of subscribers for each company, but it will result in changes for the customers themselves while giving the cable companies a more desirable geographic footprint.

"Comcast and Charter will transfer assets serving approximately 1.6 million existing Time Warner Cable customers and 1.6 million Charter customers in a tax-efficient like kind exchange, improving the geographic presence of both companies, leading to greater operational efficiencies, improved technology deployment, and enhanced customer service," the announcement said.

As for the new publicly traded spinoff (referred to only as "SpinCo" at this point), 67 percent of it would be owned by existing Comcast and Time Warner Cable shareholders. Charter's ownership group would own the other 33 percent. With 2.5 million subscribers, SpinCo would be just behind the 2.8 million served by Cablevision, which today is the fourth largest cable provider after Comcast, TWC, and Charter.

Comcast, Time Warner Cable, and Charter are all among the least liked video providers in the country, according to the American Customer Satisfaction Index. Comcast Executive VP David Cohen recently admitted in a Senate hearing on the proposed merger that Comcast is "deeply disappointed" in its own customer service. "It bothers us that we have so much trouble delivering a really high quality service level to customers on a consistent basis. It is not something we're ignoring," he said.

UPDATE: Comcast has provided details on the locations of the customer sales and swaps. The 2.5 million Comcast customers moving to SpinCo are in Alabama, Kentucky, Indiana, Michigan, Minnesota, Ohio, Tennessee, and Wisconsin. Not all customers in those states will necessarily be affected.

Time Warner Cable customers that would move to Charter in the sale and swap are in parts of Alabama, Indiana, Kentucky, Ohio, and Wisconsin.

Charter customers moving to Comcast are in parts of California, Connecticut, Georgia, Maryland, Massachusetts, New York, North Carolina, Oregon, Tennessee, Texas, Virginia and Washington state.

Editor's note: The original version of this story incorrectly stated that Charter is the third biggest cable company in the US. Cox is the third biggest and Charter is fourth.