The Guardian has this breakdown:
Public Health England provided a breakdown of how many cases were not included in each day’s figures, which are as follows:
957 cases were not included on September 25, when the original figure given was 6,874
744 on September 26, when the original figure given was 6,042
757 on September 27, when the original figure given was 5,693
none on September 28, when the original figure given was 4,044
1,415 on September 29, when the original figure given was 7,143
3,049 on September 30, when the original figure given was 7,108
4,133 on October 1, when the original figure given was 6,914
4,786 on October 2, when the original figure given was 6,968
So we can see that, at its worst, it meant that nearly 5,000 cases were missing from daily totals.