how many people did captain robert walton and his men observe on the ice sea?

Two, one man was described as very large, the other a regular sized man.

"In the middle of the ocean, on sheets of ice, they spy a sleigh pulled by dogs with a large figure driving. He disappears, leaving the entire crew in puzzled wonderment. The next day, another sleigh is at the side of the ship, on the brink of destruction amidst the ice. This time, however, there is a regular-sized human there, asking to where the ship is bound."