PWRTAQT (unshifted) is 0245-15 (shifted), a valid Volta exchange. See http://en.wikipedia.org/wiki/Baudot_code
This happens when the "shift" is lost somewhere. Or when the transmitting guy has disabled "unshift on space" for transmit and the receiving guy has enabled "unshift on space". UOS on will be the most common configuration.
If you note some senders are consistently messing up numeric exchanges, note this: In a contest some will strip out all "unnecessary" shifts thinking this will speed transmission, but what they aren't taking into account is that they will be asked for many more fills when folks are confused, and this will actually slow their rate. Making sure there is a shift at the beginning of every numeric exchange component is very wise. Some will put hyphens between numeric components rather than spaces thinking this will avoid shifts, but again this is a false economy.
There is no real confusion. Most modern RTTY software allows you to mouseover any section and see it both shifted and unshifted. If you know that part of the exchange was supposed to be numeric, just use the shifted version. Similar to when the DX sends zone 15 as "AE" in CW and you know those are cut numbers.
This is just the first level of "brain-enhanced RTTY copy". There was a very good article by, I think a JA RTTY contester, in NCJ last year, where he detailed how application of his brain plus knowledge of common callsigns and RTTY encoding, lets him pick out the correct call from garbled print.
I myself am fairly new to RTTY contesting and really enjoy it. Many contesters use multiple decoder windows simultaneously, as well as their ears and brains and knowledge of callsigns, to get correct copy under adverse conditions. It is not a mindless exercise, it is actually rather engaging to be watching a couple decoder windows and using knowledge of callsigns and exchanges while listening to the signal to get good copy.