Assessment centres are notorious for not running to time. With every intention and amazing planning in the world, they so easily fall behind schedule.
I wouldn’t worry too much about when your exercises started - it’s just about getting the amount of time for exercises like written assessments/case study prep etc.
They sent a table which was a Word document that consisted of a table with five rows (plus header):
<Time><Activity><Zoom link>
<10-10:15><Introduction><link>
<10:15-11:00><Group Exercise><link>
<11:00-11:10><Break>
<11:10-11:40><Written exercise><link>
<11:40-12:00><Written exercise><link>
(there was no other text except for the names of the staff leading the sessions)
Whereas they should have combined the last two rows into one
<11:10-12:00><Written exercise><link>
and provided further clarification:
"You will be sent a link to a skillsarena task on the day, which you will have 30 minutes to complete. You should join the zoom session before starting the task, then leave it to do the task, then rejoin again after you have completed it. "
As it was the fact that a 11:40 start time was given for the apparent second 'written exercise' zoom meeting, led to an expectation (by me!) that you would need to be back there at that time, or at least not be too late, because it was listed as a separate item labelled "written exercise"