Under the significance level=0.05, we can see that p-value=0.0<0.5 so we can reject the null hypothesis that the ratio of subscribers biking on weekends over subscribers biking on the whole week is the same or higher than the ratio of customers biking over weekends to customers biking on the whole week.  Then we can accept the alternative hypothesis that ratio of  subscribers biking on weekends over subscribers biking on the whole week is lower. And it can tell us that customer prefer riding on weekends.
Weakness:  (1). The sample size is small, the ratio may not represent the overall trend.      
                        (2). Ride duration is not considered. If some one use Citibike for 10 hours on weekdays and 1 hour on weekends, only counting ride times may not fully make sense in                                       term of date distribution.
Strength: The test model fit the problem well and it can provide accurate conclusion based on the null hypothesis.

Reference :

Citibike - Wikipedia. Link