The government and the opposition are both using 10,000 and 33,000 as the number of people reached by track-and-trace, and the estimated number of people currently infected.
The 10,000 figure seems roughly consistent with the current average of around 1,000 new cases detected daily, and an infection period of around ten days.
However, the 33,000 figure of total currently infected, detected or not, seems grossly at odds with the estimate from this model:
https://covid19-projections.com/united-kingdom
…which estimates some 190,000 currently infected. Even its lower bound is about 50,000, well above the 33,000 figure. Another predictive model:
https://covid19-projections.com/united-kingdom
…estimates over 6,700 new infections daily, detected or not, with a lower bound of over 4,800. Again taking a ten day infection period, these translate to 67,000 and 48,000 currently infectious, again both higher than the government figure.
I also have anecdotal evidence of suppression of figures imposed by management at a local hospital.
I will try to look into other mathematical models later today, but these initial indications suggest that figures are being suppressed.