Section 35 (2ab) - r&d expenses

Dear Sir/Ma'am,

I have a query w.r.t. deduction allowed u/s 35 (2AB). It says that 200% is allowed, but my query is, does that mean 200% below the PBT or 100% below PBT.

My understanding is that all expenses are deducted before PBT and after PBT 200% of R&D expenses will be allowed. but the 2nd interpretation can be 100% (actual expense before PBT) and 100% after PBT, i.e., total 200%.

Please give clarification.

thank you.

Vijay.