One of the aspects of a total return fund is that it totally returns everything to the investor down to the penny from the date of investment. The answer to your question is that you will get interest for the remaining days of October beginning on the date of purchase for that portion of your additional purchase.
Don't mean to rain on your parade but my basis is something like $8.40 beginning years ago when I started with this fund.
If you want to do is start the clock as of 1 Jan 11 you need to add the cap gain from the prior Dec. or account for all the additional shares recieved as a result of the cap gain distribution. The NAV distributios never gets accounted in NAV postings from 31 Dec to 1 Jan. Anyway "back where we started is a complete oversimplification" for the majority of PTTRX shareholders-you can't possibly think we all bought in on 1 Jan 2011 and even if so we are still Also, the adjusted close for PTTRX as of 31 Dec 2010 is $10.62 and the adjusted close for PTTRX for the first day of trading in 2011 is $10.62 so we are still ahead of the NAV game not including dividends by $0.20. Not bad for a bond fund in trying times. Or are you just all about sour grapes.