There were set fixtures on the 16 Saturdays from 5 September to 19 December.
The reverse of these fixtures were on 16 of the for 17 Saturdays in the New Year (excluding 16 January which was FA Cup First Round Proper).
No matches could be played in the months without an R - the football season ran from 1 September to 30 April.
At some time after clubs had been advised of their 32 mandated fixtures I believe there was a meeting in a smoke-filled room where club representatives agreed their remaining fixtures with the 3 remaining clubs.
The extract you have shown indicates that 9 matches were scheduled for Christmas Day - why did neither PNE nor Sunderland play? They were actually paired the previous Saturday, so the Christmas fixtures were clearly ad hoc.
Six of the nine Christmas Day fixtures were reversed on Boxing Day, with all the remaining eight clubs playing. Were Blackburn required to host Middlesbrough on the Friday and then visit PNE the next day (PNE not having played on the Friday)?
A full set of matches was scheduled for 6 February even though this was FA Cup Second Round day. In the event none of these matches was played on that date. Seven were re-arranged for later dates but three were brought forward to September. I'd be interested to know whether that was before the list you quoted was printed, or done soon afterwards.
Chelsea's fixtures with PNE were not on mandated Saturdays. Their home match was on Tuesday 1 September with the away match on Monday 7 September, after Chelsea had visited Liverpool on the opening Saturday.
Similarly Arsenal hosted Everton on Wednesday 2 September then visited Notts County on the Saturday and visited Everton on Monday 7 September.
There were six matches on 1 September and two more on 2 September, but Manchester United, Middlesbrough, Nottingham Forest and Notts County did not play until the full fixture round on Saturday 5 September.
Incidentally the listed match for Tuesday 29 December (Sheffield United v Bury) was postponed and eventually played on Monday 1 March.
There were seven matches on New Year. Their reverse fixtures comprised one on 1 September, two on Boxing Day, one on 9 April (Good Friday), two on 12 April (Easter Monday), and one on 13 April. I believe the League agreed the fixtures before publication but did not initiate them.
I'd also be interested to know whether the Sheffield United v Liverpool match was listed for the final Saturday (Cup Final Day!) because it was actually brought forward to Monday 14 September.