You can enter a total of up to six modules in the field above, using the numbers 1-7 (corresponding to the old style Modules 1-7) and letters A-D (corresponding to the new style modules).
If you have passed Module 1, you would enter 1.
If you have passed Modules 2 and 3, you would enter 23.
If you have passed Modules 4, 6 and A, you would enter 46A.
If you have passed Modules 2, 3, A, D, you would enter 23AD.
The order in which you list the Modules does not matter.
More information about the IRSE Exam is available on the IRSE website.