Cumulative sales of Microsoft’s (MSFT) first two tablet models have failed to meet expectations, according to a new report. Citing multiple unnamed sources, Bloomberg on Thursday evening reported that sales of Microsoft’s Windows RT-powered Surface tablet have reached just above 1 million units to date. According to the same sources, Microsoft ordered about 3 million Surface slates from its manufacturing partners. Sales of the newer Surface Pro model have totalled about 400,000 thus far, the report claimed. The numbers seem fairly in line with earlier estimates that suggested Microsoft would sell fewer than 1 million tablets in the fourth quarter last year.