I believe Mr Enahoro.
This year's SITP can only start in the last quarter. Shell is a multinational which knows everything about employee-employer contracts. Considering that most employers in Nigeria adopt the one month notice of disengagement policy and the minimum length of time required for a comprehensive medical examination of prospective employees, it makes sense for Shell to give its future employees at least 6 weeks to start preparing for the new challenge.
I strongly believe near-successful candidates will be called for medicals latest 3rd week of August while successful candidates (those who are medically fit) will probably get their letters latest 1st week September.