depends on the broker, but all the brokers i've ever used have amalgamated them into a single entry on the "my portfolio" or similarly titled section when you log into their online trading website. some, such as IB, will identify the individual parcels for you, but you have to run special reports to get it to do that.
but i would recommend you get into the habit of keeping records of your trades (eg. in an Excel spreadsheet) and record them as two separate parcels anyway. because they are in fact two separate entities when it comes to tax purposes. when you do a partial sell you are allowed to nominate which parcel(s) the units you are liquidating come from (
http://www.ato.gov.au/corporate/con...htm&pc=001/001/038/002/003&mnu=0&mfp=&st=&cy=).
for eg. if i bought 1000 BHP at 30 and another 1000 at 35, then i sell 1000 at 40 and want to take the capital gains hit this year because i believe that will provide the best overall tax outcome, i can opt to dispose of the 1000 that were bought at 30. but if i had bought the parcel at 35 in 2011 and parcel the 30 a few months ago, generally (but not in every situation) i would opt to dispose of the ones bought at 35 as those are eligible for the CGT discount.
if you do not have the details of the individual parcels, and you get questioned on it, the tax office may force you to use a first in, first out method, or an average cost method. either of which may, depending on your circumstances, produce a suboptimal tax outcome.
minimising the tax hit is a very important part of trading, if you haven't discovered that already, you soon will!
PS. this is not tax advice. i am not a qualified tax accountant. speak to one if you are unclear on any of the above.