Even though Hannah understands why Chris is asking the question, she doesn't agree with him.

She says, “Based on past experience (meaning her past experience, or the past experience with the company), we know that customers mostly consider 'affordability' and 'ease of use'” to decide which product to buy.

She says to Chris, “I can't go into this in detail now.”

To “go into something in detail” (detail) means to discuss or talk about something - talking about all the specific issues or problems, to talk about it in a lot of detail.

Right now, in this lesson, we're going into detail about the meaning of the new vocabulary words used at informal meetings.

We're talking about it a lot; we're giving all of the specifics.

When Hannah says she can't go into detail now, she means that she doesn't have time to explain things in detail, specifically, at this moment.

Finally, Hannah says that most customers want reliability, meaning they want the product to work, and that the design is secondary.

If we say that something is “secondary” (secondary), we mean that something is less important than another thing.

If you look at the word “secondary,” you can see the word “second,” meaning number two, so something that is secondary is less important.

Something that would be number one - that would be most important - we would call “primary” (primary).

In this case, design is less important than reliability - it's secondary; reliability is primary.

You might also say that being able to write in English is secondary if you have to speak it at your job, meaning it's more important for you to be able to speak English than to write in English, for example.