Slabs in SSI excise exemption - Following are slabs in SSI excise exemption.
First slab of 150 lakhs - There is full exemption from excise upto the first clearances of Rs. 150 lakhs, starting from 1st April every year, if the SSI unit does not avail Cenvat credit on inputs. If an SSI unit manufactures goods of different varieties, falling under different Chapter heads and/or in different factories, total exemption considering clearances of all Chapters together and all factories of same manufacturer together, will be Rs. 150 lakhs. An SSI unit can opt for paying full normal duty also.
Second slab after initial 150 lakhs - After the turnover crosses Rs. 150 lakhs, full normal duty is payable. The SSI unit can avail Cenvat credit on inputs in respect of inputs used after turnover crosses Rs 150 lakhs. - . - . - Even if an assessee crosses turnover of Rs. 4 crores, he has to only pay duty at normal rate. The SSI manufacturer does not have to pay duty on earlier turnover for which he had availed concession. [confirmed in Searsole Chemicals v. CCE 1999(113) ELT 435 (CEGAT)]. However, in next year, he will not be able to avail any concession and he has to pay normal rate of duty from 1st April itself.
Excluded turnover for calculating exemption limit of Rs 150 lakhs - While calculating exemption limit of Rs. 150 lakhs, some of turnover of SSI is not to be considered, as explained below. [Note the differences in provisions in calculating limits of Rs 150 lakhs and Rs 400 lakhs].
Clearances of goods exempted under any other notification to be excluded – Some goods may be exempt under some other notification, i.e. other than SSI exemption notification. In some cases, duty may not be payable on such goods for some other reason. Turnover of such goods is not to be considered for calculating exemption limit of Rs 150 lakhs. However, if some intermediate product gets produced, its turnover may be held as includible. [However, this turnover (except clearances to EOU, SEZ, STP, EHTP, UN etc.) will have to be considered for calculating exemption limit of Rs 400 lakhs].
I think one can avail two different notification at the same time.
For further details please refere below link.
https://www.dateyvs.com/cenex09.htm