If you bought $1000 worth of 1-year treasury bills (maturing in 12m) six months ago you have less than $1000 worth of treasury bills (maturing in 6m) today. That could be a problem if you need to recover today at least the $1000 that you put. (There may be no problem with much shorter maturities - or could be worse with bonds with longer maturity. The quote didn’t give any details.)
Par value or market value? If it’s the former the current value is surely less.