Sometimes you may have 2 different modules implementing hook_form_alter() on the same form. In that case, the order of the module execution would follow the alphabetic order of the module name. If you want to alter the execution order, you could either update the system table in database or install the Modules Weight module.
1. Download and install the Modules Weight.
2. Go to admin/config/system/modules-weight to adjust the module weight.