If the number matters to the extent that it is repeated by ministers almost whenever asked about PPE - then I might ask why not - because they must know to have come up with the figure? Without knowing how the number is made up it is rather meaningless...and if I was inclined I could flip this on it's head and suggest that you don't think it necessary as it might expose the 1bn figure as a little bit of smoke and mirrors. But I won't - as that would be getting political and so not for here.
So despite saying you're not comment further you do. As others have said there is nothing we can do to justify the figures and indeed the information you are being given. You can either choose to accept them to some degree or not. Either way how about rather than speculating on whether the government is telling the whole truth and using the thread to spin your own political views a la the brexit thread let them get on with it and judge them when we get out of lockdown and how we cope with the recovery as a truer litmus test of their ability to govern and get the economy and business back on track.