Getlayout on a pivot returns qType to "E" cells, what does that mean?

[vincent_ardiet_]

Hi,
We are using the API to build our own object and to parse the resulting JSON for our own UI.
Playing with pivots we have noticed (using QS UI or the API) that a cell (a total) was with a qType to T but was moving to E when some selections are applied (here on the field [Account L4]).
On a visual perspective this doesn't change but what does it mean? And for our JSON parsing this is quite confusing.