When it hits 100% thats means we locked in 75% of the blocks
Indeed. When 100% is reached that means 15120 out of the last 20160 blocks were voted yes. It is a little confusing perhaps, but you should just focus on the 15120 necessary blocks.
It's 95% currently and is equal to 1916 out of 2016. At this time 1404 blocks are needed to lock-in segwit and only four days are left till the end of the activation period. It's still hugely political and dependent upon pools with majority hashrate and their owners that try to tune everything up in accordance with their positions in financial markets.