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The problem is that the PHE developers picked an old file format to do this - known as XLS.
As a consequence, each template could handle only about 65,000 rows of data rather than the one million-plus rows that Excel is actually capable of.
And since each test result created several rows of data, in practice it meant that each template was limited to about 1,400 cases. When that total was reached, further cases were simply left off.
"
https://www.bbc.co.uk/news/uk-54422505
"
The problem is that the PHE developers picked an old file format to do this - known as XLS.
As a consequence, each template could handle only about 65,000 rows of data rather than the one million-plus rows that Excel is actually capable of.
And since each test result created several rows of data, in practice it meant that each template was limited to about 1,400 cases. When that total was reached, further cases were simply left off.
"
@Sam_w wins.