The City of Berkeley uses a ranked choice voting system that allows voters to choose up to three candidates for an office and rank them first, second and third. Ranking candidates is not required. Ranking the same candidate first, second and third does not give any advantage to the candidate. (See the City of Berkeley's RCV Information or the Alameda County Registrar of Voters).
Laurie is not strategizing with any other mayoral candidates around RCV and hopes to win on the first round with more than 50% of the vote. So he is urging supporters who want Laurie to win that they vote only for him as their first choice.
Laurie is asking supporters of other candidates to consider voting for him as their second choice.