[GNC] What does this mean?

[Daniel G Rodriguez]

Hi guys,

I'm new to GnuCash. In the New Book Options dialog box, the tooltip for
"Use Split Action Field for Number" says:

"Check to have split action field used in registers for 'Num' field in
place of transaction number; transaction number shown as 'T-Num' on second
line of register. Has corresponding effect on business features, reporting
and imports/exports."

Does the first part of the phrase mean:
1. 'Num' field normally uses the transaction number?
2. 'Num' field can be used as the transaction number?
3. 'Num' field is usually used to enter a transaction number?

I think it means #2, but want to be sure.

Thanks

--Daniel