I forgot to say he thinks he's going to be manager some sunny day, maybe in 1990 when it's called the Great Alexandrov and Petrooshki Tea Company or something. (9)
Sammy is talking about Stokesie here, who aspires to Lengel's job. 1990 would have seemed like the distant future to the story's readers (Stokes would be in his 50s by then), so Sammy is kind of poking fun of the modesty of his friend's ambitions. A&P is short for Great Atlantic and Pacific Tea Company; the new Russian name reflects fears in circulation at the time that the Soviets were going to take over America.
Lengel comes in from haggling with a truck full of cabbages on the lot and is about to scuttle into that door marked MANAGER behind which he hides all day when the girls touch his eye. (11)
Lengel is the story's authority figure. He has the power to decide how people can and can't dress in the store.
He didn't like my smiling – as I say he doesn't miss much – but he concentrates on giving the girls that sad Sunday-school-superintendent stare. (14)
In addition to being manager of the A&P, Lengel teaches Sunday school. These two positions give him power in his community. In the story, this is shown as the power to dictate what people wear and the power to be rude and get away with it.
Policy is what the kingpins want. What the others want is juvenile delinquency. (18)
A kingpin is the person in an organization with the most power. In the A&P that's Lengel. Sammy is suggesting that Lengel's no-bathing-suit policy is a way for him to maintain power and control in his store.
I started to say something that came out "Fiddle-de-doo." It's a saying of my grandmother's, and I know she would have been pleased. "I don't think you know what you're saying," Lengel said.
"I know you don't," I said. "But I do." (28-30)
You can imagine what Sammy was starting to say here before he wisely changed it to "fiddle-de-doo." In addition to showing Sammy refusing to be intimidated by Lengel, this scene suggests that his grandmother has helped him gain strength of character.
"You'll feel this for the rest of your life," Lengel says, and I know that's true, too, but remembering how he made that pretty girl blush makes me so scrunchy inside I punch the No Sale tab and the machine whirs "pee-pul" and the drawer splats out. (31)
Lengel tries to exert power over Sammy by using threats and intimidation. But Sammy's anger over Lengel's use of that tactic on Queenie overrides any effectiveness the threat might have carried.