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Here "intValue" is an integer of N bits from the Data Section (N=bit width of descriptor).

Example:
For pressureReducedToMeanSeaLevel "pressure" we have:
code=010051007004,  type=long (integer)
, scale=-1, reference=0, bitwidth=14

And the formula used is: value = (intValue + ref) * 10^-scale
So when we encode a value of 213.61 we do the above formula in reverse i.e.
intValue = round(value/10) - 0 = round(213.61/10) = 21
So we store the integer 21 in the BUFR message using 14 bits.
When we come to decode it, we use the first formula i.e. value = (21 + 0) * 10^--1 = 21 * 10 = 210
You So when you put in 213.61 but , you will get out 210. Precision of this element is 10^^-scale i.e. 10 so it will not store intermediate values. It will be 210 or 220 or 230 etc..

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To encode this descriptor with higher precision we can add an operator around the 007004

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as follows:

set unexpandedDescriptors = { 207003, 7004, 207000 };
set pressure = 12.34;
set pack = 1;
write;

We have added a 207003 operator that changes the scale factor, the reference and the width of the following key. Then disable the behaviour with operator 207000. Quoting the WMO BUFR table C for reference:

Operator 207YYY means "Increase scale, reference value and data width"
Description: For Table B elements that are not CCITT IA5 (character data), code or flag tables:
1. Add YYY bits to the existing scale factor
2. Multiply the existing reference value by 10**YYY
3. Calculate ((10 * YYY) + 2) / 3, disregard any fractional remainder and add the result to the existing bit width."

That way we can encode pressure with 2 decimal digits:

"key" : "pressure",
"value" : 12.34,
"index" : 1,
"code" : "007004",
"units" : "Pa",
"scale" : 2,
"reference" : 0,
"width" : 24

Note the difference with the original 007004 descriptor:

"key" : "pressure",
"value" : 10,
"index" : 1,
"code" : "007004",
"units" : "Pa",
"scale" : -1,
"reference" : 0,
"width" : 14

so we increased the width by 10 bits and changed the scale to 2.

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