are below guesses correct?
Different manufacturers use different systems for identifying products. You shouldn't look for products by that exact code unless you are not interested in products from other manufacturers and have no problems with product availability.
For a straight fluorescent tube, the key things you need to know, in approximate decreasing order of importance) include
- connector types (usually bi-pin)
- diameter (in eighths of an inch)
- length (in feet or in metric equivalent for many folk outside USA)
- colour temperature (often expressed as cool-white, warm-white, daylight etc)
- light output (lumens) or
- power (watts) - usually proportional to length.
- voltage (Usually only one variant e.g. 120V in USA, 230V in EU)
If you ask for an "two-foot warm-white T8 fluorescent-tube" you'll most likely get something that does the job.
what does t8 mean?
As Jimmy stated, it refers to the diameter of the tube in eighths of an inch. The T8 designation is for fluorescent tubes with two pins at each end.
would it be possible to provide higher watt alternative?
Generally no. You usually need a longer tube to produce more light.
Note that nowadays, wattage is useless as an indication of light output, you should look for lumens instead. Wattage just tells you how much heat the tube (or bulb) puts out.
Fluorescent tubes are still pretty good at light output. In my local store recently, the tubular LED fixtures had lower light output than the same sized (but cheaper) fluorescent fixtures. The key is to always check or compare the light output rating in lumens.