I believe that as you get stronger than 3.2% the bee damage becomes greater, with less than 3.2% the efficancy is reduced.
I suspect that the reason for supply as 4.5% is because once the sugar is added to the solution it becomes subject to degradation with time. Your soulution kept in cool dark conditions will probably be good for years.
I suggest that you either inquire from your supplier - BKA - what was intended.
Having read the instructions on the packet of OA from Thorne, which state: 75g OA crystals (technical), 1 litre water and 1 kg sugar will give a 3.2% solution. I suggest that the solution you have is good and only needs the requisite amount of sugar to bring the solution to the required 3.2%. be warned though that this is an uninformed guess. Your supplier should be able to confirm this is the case.
In the Thorne recipe they state that the amount is good for 25 hives, so a quarter of your solution would be good for half a dozen hives. Be aware of the discrepancy caused if you have only 1 litre, rather than 1 litre + 75g (would that be 1.075 litres).
Failing that, Rouary on the BBKA forum or Finman and others here should be able to work out reliable figures. Is PH an industiral Chemist or just a roughneck? ha ha - no offense intended
I'm sure that the relevant advice is available from a few knowledgeable souls. best to ask your supplier though as they are almost certain to have an unequivocal answer for you.
Sorry to go on a bit folks.