RPG - what is += here?

Question

Can you explain what the += means in this statement?

Eval      AssGr2Pun += FinQty#        

Here is the rest of the code for context:

 Exsr      FinItmTot                 
 Eval      AssGr2Pun += FinQty#      
 If        OrderAdd = 'N'            
 Eval      Gr2TPass += 1             
 Eval      OrderAdd = 'Y'            
 Endif                               
 Eval      AssGr2Pst += 1            
 When      OhReqd = Today            
 Exsr      FinItmTot                 
 Eval      AssGr2Tun += FinQty#      
 If        OrderAdd = 'N'            
 Eval      Gr2TTday += 1             
 Eval      OrderAdd = 'Y'            
 Endif                               
 Eval      AssGr2Tod += 1            
 When      OhReqd = Tomorrow         
 Exsr      FinItmTot               

Answer 1

This is an assignment operator.

Where <target> <assignment operator> <expression>:

• = The expression is assigned to the target
• += The expression is added to the target
• -= The expression is subtracted from the target
• *= The target is multiplied by the expression
• /= The target is divided by the expression
• **= The target is assigned the target raised to the power of the expression