SELECT "Sample size" FROM table_67346 WHERE "Date(s) administered" = 'june 30, 2010'
How many people were surveyed in the poll from June 30, 2010?
CREATE TABLE table_67346 (
    "Poll source" text,
    "Date(s) administered" text,
    "Sample size" text,
    "Margin of error" text,
    "Jerry Brown (D)" text,
    "Meg Whitman (R)" text
)