I can't understand "frequency drift temperature coefficient +0.4 % / C". What is it?

If stated frequency drift 0.4% per C, how to calculate drift at 2.4GHz?
For example, change temperature by 50C, then 0.004*50=2%
And then, what to do with that 2%?

2400000000 Hz + 2400000000 x 0.02 = 2880000000 - it seems not okay =) So how to calculate frequency drift using this number of 0.4%/C..?

I think you made a mistake.

2,400,000,000 + 2,400,000,000 x 0.02 = 2,448,000,000

I still do not get that...

0.4 [%/C] * 50 [C] =20 [%] = 0.2

2,400,000,000 + 2,400,000,000 x 0.20 = 2,880,000,000

isn't it too much? 2.4Ghz->2.88GHz

0.4 %/°C calculates to 20% over 50°C, as correctly stated in post #3.

But you didn't tell for which device the specification is given.
So if you ask "isn't it too much?" Yes, possibly. It depends.
Maybe it's just a typo.

ha-ha! i did not read datasheet well, just searched for drift =) it was RC Oscillator parameter. Device is CC2500 with PLL.