Whilst the number is extremely impressive, contrasted with 50 days for the S3 and five months for the S2, it’s important to note that Samsung is quoting shipments rather than sales. As The Verge observes:
The figure is controversial because shipped phones could theoretically be waiting on store shelves without having been purchased by customers. In comparison, when Apple announced it sold 5 million units of the iPhone 5 in its first weekend, it was referring to actual sales to end users.
The mixing of sales and shipments can often make it difficult to make direct comparisons between competing devices, especially as deals are often struck which require carriers to commit to buying large quantities of top-selling handsets in order to achieve volume pricing, and there is no way to know how many of these pre-agreed sales have been shipped at any given point.
However, it’s likely that carriers will have agreed phased delivery schedules in line with anticipated needs, suggesting that sales will not be lagging too far behind shipments.