Grid sorting negative numbers

I’m having problems in an established grid app where negative numbers (with - in front) are sorting by their abosolute values, seemingly ignoring the minus sign. The values -0.90, -1.49 and 5.16 are sorting in that order, whereas they should be -1.49 (being the smallest) then -0.90 and then 5.16. The column header td contains class=" table-sortable:numeric" and I don’t know what else to verify. Please step me through additional verification of settings and/or steps to enable this.

thanks in advance,
Richard Adamson

Please check if your column has “int” sorting type … ting_types