It means they must be able to see into the future.

Yesterday, they needed to know what will happen today and tomorrow. Today is too late: they wanted the information yesterday.

Similarly they don't want today's sales figures today, but need to know what will happen tomorrow, because they are managers. Will they need extra staff to cope with demand, and will they run out of stock?

Associated with this use of 'yesterday' is the idiom

> I need this done by yesterday!

From [Farlex](https://idioms.thefreedictionary.com/need+(something)+yesterday). Here, it means *immediately* or *as soon as possible*.