Finding Transformer Leakage Impedance from S/C, O/C and Winding resistance tests
You can split the overall leakage inductance into two parts proportional to the turns ratio squared. For instance, you know that if the transformer was 1:1 the leakage inductance would be shared equally between primary and secondary .

You also know that if the turns ratio was (say) 10:1 and you measured a 1 mH total leakage (referred to the primary) you could attribute all of this 1 mH to the secondary by dividing it by \$(10:1)^2\$. In other words 10 uH on the secondary is equivalent to 1 mH on the primary.

So, whatever your combined leakage is referred to the primary (let's assume it to be 1 mH), split it into two halves and keep 0.5 mH at the primary and transfer 5 uH to the secondary.