On 5 September 2017, the Government published data for the number of high rise residential buildings in England (as of 31 August) with various types of ACM cladding, and with various types of insulation:
The number of buildings accounted for in this table is:
81 + 107 + 8 + 21 + 12 = 229.
The total number of buildings in England with ACM cladding (including those stripped post-Grenfell) is given in paragraph 5 (and also in paragraph 8):
Since 173 + 16 + 89 = 278, it is clear that 278 is the number of buildings as well as the number of samples.