Thanks @alexej996 for the quick response. I’ve been away on holiday for the past few weeks so sorry for taking a while to respond.
The logic makes sense to a certain degree. Any purchase of less than 0.03 BTC will mean the buyer incurs a greater deposit than that of the actual purchase. One must purchase over 0.03 BTC to see the deposit become less than the desired transaction. Then an offer to purchase 0.5 BTC has the same deposits, in this case the seller will lock in 0.501 BTC and the buyer only 0.03 BTC. Whilst I understand the requirement for a deposit to encourage the transaction to complete, it seems strange to have picked these seemingly arbitrary values as opposed to %age values based upon that of the transaction.
Either way the barrier of entry remains for those wishing to make small speculative purchases in order to build trust in the exchange, which to me seems to be counter-productive in terms of encouraging adoption from new buyers and sellers.