The orders were retried to be placed as long as an Eservice unavailable answer were received. In case you dont get an Eservice unavaialble, you get either an order ID, or a type of undefined answers (assuming that your order input is correct, if not you can get other tyes of error messages). In the undefined case you dont know what happened to your order and you need to check your open order and/or trade history lists. In the undefined case the next order was placed, unknown orders were checked in one go at the end.

Getting to numbers to which you refer. For the list of 100 orders to be placed, a total of 182 calls had to be made due to having to retry to place orders when receiving a total of 82 Eservice failures.

This leaves 100 calls (please note the difference between calls and orders, even though their numbers are equal) which did not receive an Eservice failure. From these calls, 51 received an answer which included order ID and other info. This leaves 49 calls where the answers was undefined (as said some were later found in the order or trade list, but some were also not placed).

So in the end 51 of 182 calls yielded an order ID = 28% of calls giving a correct answer.

Counting only Eservice failures as errors the error percentage is 82/182 = 45%
Also counting calls of the undefined answer type as error increases the error percentage to 71.9%

I hope this answers your question