I can clarify the following because I witnessed them:
- Sample counting was done at the counting centre
- Ballot boxes were not reopened (after they are sealed at 07:45 before the start of polling) at the polling centres.
- When ballot boxes arrived at the counting centre, they were distributed to the counting tables such that each table had boxes from different polling centres.
- Counting agents were asked to witness the opening of the boxes.
- Ballot papers were then poured onto the counting tables in full view.
- CAs were then shown the insides of the boxes and the covers.
- The centre IC then asked the counters to toss up the ballot papers so as to get a more random sampling.
- That done, the counters were told to take out 100 papers from their table at random. Table ICs supervised the process.
- These 100 were then sorted among the parties.
- Each table IC announced their count to the Centre IC in front of the CAs.
- The Centre ICs collated the results and reported them to the constituency IC.
- Counting of all the ballots started after the report was made.
I hope this helps.