11,000 positive Covid tests will be announced on Thursday due to a lag caused by system maintenance.
Public Health Wales (PHW) said their figures for the past few days are a “significant under-estimation” and they will be higher on Thursday as a result.
On Wednesday it was reported that 30 people have died with coronavirus in Wales, while there have been another 530 cases.
This takes total to 103,098 cases in Wales since the pandemic began.
PHW’s Wednesday figures take the total deaths in Wales to 2,921, with 6,193 tests carried out on Tuesday
The latest numbers follow an announcement on Wednesday that Wales will go into lockdown from 28 December.
PHW said: “Today’s figures only include a very small number of results from tests processed in the Lighthouse Laboratories and therefore represent a significant under-estimation of the true picture. We ask everyone who is using these figures to be fully mindful of this caveat.”
The seven-day case rates are being published accounting for a time lag of four days, allowing for late results to be included, which PHW said will improve the accuracy of its dashboard.
Eight of the deaths reported on Wednesday were from the Cwm Taf health board area, seven from Cardiff and Vale and six from Aneurin Bevan.
The Hywel Dda health board area reported three, whilst Betsi Cadwaladr, Powys and Swansea Bay all reported two each.
Acute patients from Powys are usually treated across the border at hospitals in England, so deaths of Powys residents usually only appear in registrations reported later by the Office for National Statistics (ONS).
Those ONS figures – which are higher – also count both confirmed and suspected cases of Covid, as well as deaths in all settings, including care homes, hospices and people’s own homes.
PHW reports new deaths daily, but these are usually from previous days.
Find out how the pandemic has affected your area and how it compares with the national average:
If you can’t see the look-up click here.
The postcode search has been updated to replace data for health boards in Scotland with data for local councils. In England, data for county councils has been replaced with data for district councils. Figures for boroughs and unitary authorities remain unchanged.