Which output data type to choose in QGIS SAGA Raster Calculator in Batch Mode?

I have 5 years of MODIS13Q1 NDVI .tiff images for time series analysis. I want to multiply all the images with the scale factor of 0.0001 before using them. In order to process all at once I try to use Processing Toolbox -> SAGA -> Grid-Calculus -> Raster Calculator in Batch Processing Mode. As MODIS13Q1 is a 16 bit signed integer I couldn’t decide which output Data Type I should choose?

The choices are:

• bit;
• unsigned 1 byte integer;
• signed 1 byte integer;
• unsigned 2 byte integer;
• signed 2 byte integer;
• unsigned 4 byte integer;
• signed 4 byte integer;
• 4 byte floating point number;
• 8 byte floating point number;

It’s suppose to be a floating number but should I choose 4 byte or 8 byte?