In their paper, "Multifactor explanations of asset pricing Anomalies (1996)" Fama french states in Table 6 that they observe a Momentum effect in their 12-2 portfolio because If I look at the worst portfolio it keep being bad and the good ones keep being good if you look over the span of one year. Alternatively the reversal portfolios have the opposite effect over the span of -5 year to -1 year.
I think that I do not understand how they capture that, first I am not clear of what "Portfolio Formation Months" mean. On top of that If I compare both Momentum blue rectangles we can notice an increase by reading from left to right that repeats in the next period I don't understand how they see momentum or reversal across time
Overall I think I have trouble understanding this table.
Note: That I have put a drawing of the 1 year momentum and -5 to -1 year reversal effect below the table.