I checked that the current price for Dec is low and we can get 1300 dec for $1 and 1000 dec is worth around $0.73 so price is low and not the right time to burn for SPS. Right?
On the other hand if dec price is high which is more 1k tokens worth more than $1, it can be good time to burn for SPS and one can earn this way. Did I say it correct?
Yes, that is correct. You always get back 975 DEC for 1 USD of SPS. If now 975 DEC are worth more than 1 USD, you can buy more SPS than you burned before.
This makes sure that the DEC price would not increase too much and is considered rather stable. However, so far we only reached this point a handful of times at max since the logic has been implemented that way.