We multiply the contamination estimate by a data-driven coefficient to take into account the low strangeness yield in the Monte Carlo compared to **data** [24]. The coefficient is derived from a fit of the discrepancy between **data** and Monte Carlo strangeness yields in the tails of the DCA XY distribution which are predominantly populated by secondaries. The factor has a maximum value of 1.07 for tracks with p T < 0.5 GeV/c and is equal to 1 for p T > 1.5 GeV/c. This factor is included in the Contamination entry in table 3.