It seems to work if you follow the Easy Step process rather than Forms entry. Just click through everything from the start of the basic info entry until you get to the last question of the profile section which asks whether you paid by installments. When you select Yes, you enter the amount there. You can then go back to forms and it shows on the Detailed Summary sheet, although oddly, still not at line 47600n on T1 General!!! Go figure!!
Although the Help says you can enter the value on line 47600, you cannot. You have to go back to the Easy step and in your Profile questions one asks you about CRA Instalments and you enter the value there.