A bicycle lane is a designated traffic lane for bicyclists, marked by a solid white line, typically breaking into a dotted line ending before it reaches the corner. Different from a simple white line showing the edge of the road, a bicycle lane follows specific width requirements and is clearly marked as a bike lane.
Treat a bicycle lane the same as other traffic lanes.
Do not turn into the lane if there is a bicyclist in the bike lane.
Do not obstruct bicycle traffic by reducing the width required for safe bicycle passage, typically 3 to 4 feet.
It essentially means 'do not get closer to a cyclist than 3 or 4 feet' (while driving in a motor vehicle, naturally).
I would suggest that the intended meaning is would be achieved by replacing "required" with "available". In other words, ensure that even if one's vehicle obstructs part of the lane, there will still be a path 3-4 feet wide which is safe and free of other obstructions. If the entire width of the lane could be used safely but for the presence of one's vehicle, then one's vehicle should be 3-4 feet from the far side of the bicycle lane; in areas where snow, debris, or other hazards would render part of the bike lane unusable, then one should ensure that one's vehicle does not reduce the usable portion below 3-4 feet.