Understanding about gain of an antenna

Guys I am having problem in understanding Gain. 3D maximum gain is 1.18*e^+001 and 2D gain at theta=0 deg is about -12 db for all phi values. As shown in the pictures. Why there is difference? also what is the meaning of the term e^+001. please elaborate.

Regards,
Rizwan

-1.1848e+001 = -11.848, no big difference to -12, isn't it?

but value of e^1=2.71 and is that gain is acceptable. It is very small. How can we enhance gain. i use PIFA antenna with dimensions of 30*30 mm with a shorting post 10 mm. The frequency response is as follows.

You are simply misunderstanding the scientific number format. e+001 means 10^1, take at look at the Windows calculator display or a spread sheet calculator.