What would the formula to convert decimal to hours be?

We're creating a new infolet in OTBI for users to see their flexi balance, however it currently displays the balance in decimal (e.g. 30.8, 1.2, etc.) when we need it to display in hours and minutes (e.g. 7:24, -10:15, etc.).

We've tried adding formulas onto the Absence Balance column (which generates the current balance) to amend this, but it always generates an error, no matter what formula we use - example pictured.

Can anyone provide the formula that would be required to insert here to convert the Absence Balance into Hours and Minutes?

Thanks.