RFE-RR to Initial Review and then to Post decision activity as reopened

I have got RFE for my H!-B extension and before submitting the documents I had to travel out of the USA.

At the time of submission of docs, processing is made premium. Now, the visa status is changed to 

1) Initial Review:

On April 30, 2014, your Alien Registration Number was changed relating to your I129, PETITION FOR A NONIMMIGRANT WORKER

After 2-3 hours, again the status changed to

2) Post Decision Activity

On April 30, 2014, we mailed you a notice informing you that your I129, PETITION FOR A NONIMMIGRANT WORKER, was reopened.

Has anyone experienced this status change? What could be the possible reason for the same?

Please help.