Straight from the Wiki:
KFLBTS_0_A - requested lambda for component protection when calculated EGT is above TABGBTS, scaled by FBSTABGM.

Note that lambts also modified by [KF]DLBTS and KFFDLBTS:
lambts = KFLBTS + ([KF]DLBTS * KFFDLBTS).

Therefore, setting KFLBTS to 1 where you don't need it won't disable bts, you also have to set KFFDLBTS = 0 to disable bts completely.[22]
Note that Mbox has DLBTS (2D), not KFDLBTS (3D).[23]

TABGBTS - Threshold for KFLBTS. Unless calculated EGTs are above this threshold, KFLBTS is ignored.

You may have to lower TABGBTS if you have a scaled MAF, since calculated EGTs will be artificially low.
FBSTABGM (0x150C2) - KFLBTS multiplier. Make sure you change the axis properly to represent your lowered TABGBTS. Again, not necessary if you have a properly scaled MAF.

You're multiplying it by 0.5, so you're halving it. 
lambts = KFLBTS + ([KF]DLBTS * KFFDLBTS).
FBSTABGM (0x150C2) - KFLBTS multiplier.

So it's basically:
lambts = KFLBTS*FBSTABGM  + ([KF]DLBTS * KFFDLBTS).

Take some values and work it out, it'll make sense.

Trying to get to grips with this and i feel like I'm failing as soon as i go near the multiplier for KFLBTS and include that in the formula.

Juts taken some numbers using KFLBTS 0.9376 + (1.4141 * -0.0156) the last part being KFDLBTS * KFFDLBTS.

This gives me 0.9149 which seems a realistic figure.

when i use the other formula KFLBTS*FBSTABGM + + ([KF]DLBTS * KFFDLBTS) with the same figures apart from multiplying by 0.5 which is taken from KFLBTS multiplier when EGT is 920C

(0.9376*0.5)+(1.4141* -0.0156) = 0.4464 which doesn't seem realistic.

Am i using the values from the wrong parts of the multiplier tables and or KFLBTS and KFDLBTS?

Attaches is a screen show of the tables I'm looking at - apologies it's the only way i know to add a photo. Really hoping I'm not just being super thick but i fear that will be the case.

(0.9376 + (1.4141 * -0.0156) -1) * 0.5 + 1= 0.95777