Random sample: holdout & segments

I'm trying to send an email campaign that includes a 10% holdout, and then splits the remaining 90% into two equal segments to receive the A/B versions of an email. What's the best way to do this in the smart campaign?

Should it be set up like this?

Step 1: Send Email

• Choice 1: IF random sample is 10%, then do nothing [my holdout group]
• Choice 2: IF Random Sample is "45%" then Send Email A
• Default Choice: Send Email B

or like this?

Step 1: Send Email

• Choice 1: IF random sample is 10%, then do nothing [my holdout group]
• Choice 2: IF Random Sample is "50%" then Send Email A
• Default Choice: Send Email B