0.5 shouldnt be an issue thou dont take my word for it .

usually the 19v will be immediately buck converted down to 12v or even lower so it shouldn't matter
 

Guys but using 19.5v output adapter for long run it may cause severe damage to my laptop??

Like ty_ger07 and Halo mentioned, it should be fine, 19.5V is in the 5% general tolerance. It's only if the 19.5V is outputting a higher voltage due to production variance, that the designed device for it could tolerate, since the designed device for 19.5 would allow for a slightly higher voltage, say 20.47V, but our laptop, estimating, should max out at 19.95V Again, I'd use a multi-meter on it before you plug it in to check the DC voltage output, and while you're at it, check your current adapter too and compare voltages, and if it's within 5%, go for it (but I wont be responsible for any damage! I don't know what the voltage tolerance is for our SC17's, could be 3-10[+/-]%, etc...)
 
Odd though, I thought the 980M and 1080 got the standard 19.5V adapter while the 1070 users got the 19V adapter.

ExplodingSidewalk
I have a EVGA SC17 P/N: 768-41-2633-T1 and was wondering if the following would work as a backup ac adapter:

NEW Genuine OEM Dell AC Power Adapter 240W 19.5V 3.5A Charger GA240PE1-00 0FWCRC


Thanks for your help.

Have you read this thread? The Dell M6800 charger has definitely been used by some users for at least 8 months without issue. The one you chose, who knows.