Better column summary descriptions

Using the FlyMine
Organism -> transcripts
template and the column summary on transcript length I realise the column summary
is doing something subtley different from what one might expect:

- while there are 34,428 rows it reports that there are 7538 transcript lengths.

This should be changed to "7538 distinct transcript lengths" or perhaps better:

"7538 distinct transcript lengths for 34,428 transcripts"