Cap of Rs. 50 lacs for filing return in ITR 1 - Is it gross or taxable income

The cap for filing return using ITR 1 is Rs. 50 lacs.  It is mentioned as Total Income. 

Whether it refers to Gross income or taxable income - after allowing exemptions under Section 10.  For example, one's gross receipts are Rs. 54 lacs and after removing - say Rs. 20 lacs received as Gratuity as per Act, the taxable income would be Rs. 34 lacs only. In such case, whether he has to use ITR 1 or ITR 2.  Pl clarify