Just remember SMART. Specific Measurable Action based Reasonable Time Based Not sure allowing a 5 min error would be beneficial since the target behavior would be telling the correct time. Goal: In 36 instructional weeks, given a picture of a clock, student will accurately tell the time with 85% accuracy. Then you could have objectives that build toward the goal. Ex: In 18 instructional weeks, when presented a picture of a clock, student will tell the correct time within 5 minutes 85% of the time as measured by the sped teacher. Your goal should be the desired outcome. Objectives can be "building blocks" so to speak.