I guess the procedure to recapture the time for new H-1 is the same as extension.
To recapture time stay out of US, you need to provide the proof of the period you were out of US, such as:
The stamping with date on your passport while you passed US or foreign country's immigration gate (for instance, 中國邊防的入境章和CIS的入境章).
Then you need to mention it in your cover letter and list the start date and end date of all the period you were out of US, then calculate the total time you claim to recapture. Finally you need to provide the new H-1 expiration date (including the recaptured time) in the I-129 form.
At first, CIS gave me a wrong expiration date in its approval. Later my attorney send a mail to reopen the case to change the exp date. Finally CIS resend me the apporval notice with the expiration date I expect.
If you still have questions, drop me a line: fritz_nj@hotmail.com.