Counting agents have a number of important roles to play at the count:
they observe the counting process and make sure that it is accurate
they can draw to the attention of count staff any doubtful ballot papers
if they disagree with a decision by the Constituency Returning Officer (CRO) to reject a ballot paper, they can ask the CRO to mark on the ballot paper rejection objected to
if a count is suspended for any reason or there is a break in the proceedings, counting agents can add their seals when the CRO seals the ballot boxes and envelopes
The CRO may issue you with information on the procedures to be followed, including instructions on what people attending verification and count can and cannot do. You should comply with any instructions that the CRO has given.