Receiving this error when trying to schedule this class.  

line: 6, Column: 41
Dependent class is invalid and needs recompilation: Class UpdateCSBHSchedulable : Static method cannot be referenced from a non static context: void updateCurrentStatusBusinessHours.updateBusinessHours()

I added the bold when I got an apex time limit exceeded error when trying to run - I read that I needed to change to a future method, but I wasn't sure of everything that needed to be changed. Are there other parts I need to adjust to make this a valid future method, and clear the 
"Static method cannot be referenced from a non static context" error?

Class below:

public class updateCurrentStatusBusinessHours
{
    @future
    public static void updateBusinessHours()
{
    
     List<SBQQ__Quote__c> SBQQs = [SELECT Approval_Status_Start_Time__c, Status_Start_Time__c FROM SBQQ__Quote__c 
                                  WHERE  RecordTypeId IN ('012U00000001s4PIAQ','0120B0000001w3OQAQ', '0120B0000001w3JQAQ','012U0000000EB4BIAW') AND
                                         Opportunity_Stage__c != 'Closed - Won (100%)' AND Approval_Status_Start_Time__c != null AND Status_Start_Time__c != null];        
     System.debug(SBQQs);
        
        BusinessHours BusinessHoursId = [SELECT Id FROM BusinessHours WHERE IsActive=true AND name= 'CSS' LIMIT 1];
     for (SBQQ__Quote__c SBQQ : SBQQs)
    { 
        //Input
        Datetime ASST = SBQQ.Approval_Status_Start_Time__c ;
        Datetime SST  = SBQQ.Status_Start_Time__c;
        
        //Approval Status Calc
        Decimal ASSTdiffHours = BusinessHours.diff(businessHoursId.id, ASST, system.now());
        Decimal ASSTdiff = ASSTdiffHours/3600000;  // converting milliseconds into Hour
        
        //Status Calc
        Decimal SSTdiffHours = BusinessHours.diff(businessHoursId.id, SST, system.now());
        Decimal SSTdiff = SSTdiffHours/3600000;  // converting milliseconds into Hours
    
        //Output
        SBQQ.Approval_Status_Business_Hours_CST_SF__c = ASSTdiff;
        SBQQ.Status_Business_Hours_CST_SF__c = SSTdiff;
        SBQQ.Last_Current_Status_Run_Time__c = system.now();
    }
        //Update all records
        update SBQQs;
        
  }
}