Knowing Andrea, it was probably an encyclopedia.

[diamondcutter]

“Guess what I bought with my own money?” this girl with curly brown hair named Andrea Young whispered to her crybaby friend Emily. Knowing Andrea, it was probably an encyclopedia.
“What did you buy?” asked Emily.
“An encyclopedia!” Andrea said, all excited.

Source: My Weird School 16 - Ms Coco Is Loco, Dan Gutman

Does the last sentence mean #1 or #2?
1. I know Andrea well and it was probably an encyclopedia.
2. If you know Andrea, you will know that it was probably an encyclopedia.

 

[emsr2d2]

“Guess what I bought with my own money?” this girl with curly brown hair named Andrea Young whispered to her crybaby friend Emily. Knowing Andrea, it was probably an encyclopedia.
“What did you buy?” asked Emily.
“An encyclopedia!” Andrea said, all excited.

Source: My Weird School 16 - Ms Coco Is Loco, Dan Gutman

Does the last sentence starting "Knowing Andrea" mean #1 or #2?

1. I know Andrea well and it was probably an encyclopedia.
2. If you know Andrea, you will know that it was probably an encyclopedia.

Since the reader doesn't know Andrea, it can only mean that Emily knows her well and thinks that the likely answer is "An encyclopaedia".

 

[Tarheel]

@diamondcutter Which sentence needs a comma (before "and")?

 

[diamondcutter]

Hi, Tarheeel. Do you mean #1? All of the following patterns are acceptable, aren't they?

a. I know Andrea well and it was probably an encyclopedia.
b. I know Andrea well, and it was probably an encyclopedia.
c. I know Andrea well. And it was probably an encyclopedia.

 

[Phaedrus]

“Knowing Andrea, it was probably an encyclopedia.

. . . Does the last sentence mean #1 or #2?
1. I know Andrea well and it was probably an encyclopedia.
2. If you know Andrea, you will know that it was probably an encyclopedia.

It means #3:

3. My knowledge of Andrea leads me to believe that it was probably an encylopedia.

 

[Tarheel]

Hi, Tarheeel. Do you mean #1? All of the following patterns are acceptable, aren't they?

a. I know Andrea well and it was probably an encyclopedia.
b. I know Andrea well, and it was probably an encyclopedia.
c. I know Andrea well. And it was probably an encyclopedia.

The first sentence does not fit the way it would be spoken. As for the third one, maybe you could use that if there was an extra long pause after well. (Unlikely.)