The Retries Histogram shows the number of MPNs in each stage of the retry schedule and all of the retries defined for the survey.

The black bars represent the accumulated amount of respondents to be called in a particular retry.

The grey bar represents a group of respondents who have been called. They are in stand by because surveda is still waiting for their answers, once the answers or waiting time are completed the respondents will move to black bars or drop from the histogram, depending on their dispositions.

All the respondents are documented in the same histogram, so it's likely to have respondents from an earlier batch being called for their second retry at the same time as respondents from a later batch being called for their first retry.

As the survey progresses, the retry batches will be smaller as the completed, rejected, and ineligible respondents will exit the survey.

For SMS and Mobile web there's a defined time window to receive the last answer. When that time window is completed the batch of respondents will be shown in red as in the image below.