Has phosphatase activity with the synthetic substrate 6,8- difluoro-4-methylumbelliferyl phosphate (in vitro) (PubMed:24531476, PubMed:29121083). Has almost no detectable activity with phosphotyrosine, even less activity with phosphothreonine and displays complete lack of activity with phosphoserine (PubMed:29121083). The poor activity with phosphotyrosine may be due to steric hindrance by bulky amino acid sidechains that obstruct access to the active site (PubMed:29121083). {ECO:0000269|PubMed:24531476, ECO:0000269|PubMed:29121083}. This is the function of Ensembl gene identifier ENSG00000188542 (DUSP28, dual specificity phosphatase 28).