It suggests that the 4th wave of an impulse would fall below the lower of the "Acceleration Channel" before it would be complete. When counting waves (1) and (2) of C(circle) of B as shown in the chart, and drawing the channel from their extremes (using the assumed top of wave (3) as the channel's top coordinate) the 4th wave-looking correction between December and March did not fall below the channel. It did fall below a more narrow channel made from an assumed later-occurring smaller degree 1st and 2nd wave, which leads me to suspect that the index is just hitting it's wave (3) now and will decline in wave (4) to below this channel (perhaps to .236 or .382 of wave (3), where the red box is) before rising again in a wave (5) at least slightly above this wave (3) to complete "C" (circle) of B of IV.
When wave (4) develops, its parameters could provide the guidelines for drawing the descending "Deceleration Channel" which would be useful in determining where wave (5) begins.
It could indicate the end of the rally (at least for now), if we interpret the January-February action as the 3rd and 4th wave and the subsequent rise until now as an extended 5th wave with five internal waves now complete at this level.