请问 2019 MOCK B 下午卷case 的第四题：
提干：All of Robinson’s accounts have given him full discretion in managing their funds. Given his decision to purchase Paladin, he determines the total number of shares that need to be purchased for all of his accounts and submits the block buy order to Marietta’s trading department. It takes several hours to fully execute the trades, and the shares are allocated according to Marietta’s Trade Allocation Policy. The policy states, “Client accounts participating in a block trade shall receive the same execution price and be charged the same commission, if any. All trade allocations shall be made on a pro rata basis prior to or immediately following a partial or complete block trade.”
首先答案说这个做法是不违反的，原因是There is no violation. Standard III(B)–Fair Dealing states that members must deal fairly and objectively with all clients regardless of whether they are discretionary or non-discretionary accounts. Marietta’s trade allocation policy treats all clients fairly in terms of both trade execution order and price.
请问提干的画横线如何理解，尤其是后半句prior to or immediately following a partial or complete block trade，这个是什么意思那？能用中文讲一下吗?thanks！
