Inline editing 4.2 appearing as 4.1999998

Using datatable and Editor (in line) to allow a user to enter sample results.

Numbers such as 4.2 are being stores correctly in MY MSSQL DB but being displayed with a floating point error (I assume). Anywas I've got found the initial display by using ColumnDefs on the Datatable:

        columnDefs: [
          {
              render: $.fn.dataTable.render.number(',', '.', 1),
              targets: [3,4,5,6,7,8]
           }
        ],

which is great, however when I click in the 4.2 Aspergillus in the 2nd row I get:

Is there something similar to the columnDef for the datatable I can use? or is there another solution to get it to be 4.2 instead?

Thank you inadvance for any help given