I know that going in - meaning in context

Question

I watched Seinfeld yesterday and I couldn't understand one of the responses of Jerry (A punch line). He says:

"I know that going in."

Who is going in where? Why the present simple?

Here is the full portion so you will get the context (The sentence is at the end of it):

KRAMER: Jerry. This is great cantaloupe.

JERRY: Alright.. (tastes it)

KRAMER: Ah, huh. It's good?

JERRY: It's very good.

KRAMER: Good, huh?

JERRY: Good.

KRAMER: I got it at Joe's.

JERRY: Uh-Huh.

KRAMER: Forty-nine cents a pound. That's practically half than what you're paying at the supermarket. I don't know why you don't go to Joe's.

JERRY: It's too far.

KRAMER: It's three blocks further. You can use my shopping cart..

JERRY: I'm not pulling a shopping cart. What am I suppose to wear? A kerchief? Put stockings on and roll 'em down below my knee?

KRAMER: See, the other thing is, if you don't like anything, he takes it right back.

JERRY: I don't return fruit. Fruit is a gamble. I know that going in.

Answer 1

The phrase is short for something like

I understood the potential consequences before entering into a hazardous situation.

Seinfeld's humor is often about exposing the absurdities of ordinary human life, things that we normally overlook as normal or routine. In this case Jerry implies that buying fruit is akin to some dangerous but potentially thrilling activity. Sometimes the fruit is good. Sometimes it's not. He doesn't know, but he's willing to take that risk.

It's funny, because it's just fruit. There is no real danger. The more common use of this phrase might be in something like buying cryptocurrency, where there are substantial risks:

A: I can understand investing in BitCoin, but some of those others are shady as heck. You could lose everything.
B: Yeah, I know that going in. I'm willing to take the chance.