“I've had a tap into some of our competitor's phones. They've been getting careless with their burners recently. It seems the architectural plan for a certain well-known financial institution is going to be changing hands at a parking lot in Pillbox Hill. Could you persuade them to part with it? They'll have a lot of heat so probably best to split up your guys. Put some snipers on the roof while the rest go in for documents. Good luck.”
Lester hacked the phones from a rival crew and he's now informed that they are having a deal with an architectural financial institution at a parking lot in Pillbox Hill. Lester advises that one player should snipe the enemies from a higher building meanwhile the other guys collect the document. After all the enemies are dead and the team has the document, the document needs to be delivered to Lester's warehouse in Murrieta Heights, and the job is complete.
Go to the parking lot.
Climb the ladders and get in position.
Take out the enemies.
Get the document.
Deliver the document to Lester's warehouse.
GTA Online - Mission - The Parking Garage Hard Difficulty
The mission title could be a reference to the episode "The Parking Garage" on the NBC Sitcom Series Seinfeld.
The Stunt Jump on top of the Parking Lot in this mission is barricaded, presumably to not make the escape too easy.