The number of optical isomers of 3,4-dichlorobutan-2-ol

The number of optical isomers possible for the given organic molecule is? $$\ce{CH_3-C^*H(OH)-CHCl-CH_2Cl}$$ (the configuration is fixed at $$\ce{C^*}$$)

The given answer is 2. The carbon marked with an asterisk is chiral, and the carbon to the right of it is also chiral. Doesn't that give 4 isomers? What does "configuration is fixed" mean?