Is it normal for the curvature of a cold coke oven to be negative?

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One of our coke ovens is about to be ignited for heating up, but currently, the calculations regarding the curvature of the cold oven show negative values for the curvature of certain oven columns, and these values are quite large. (The calculation formula is: upper line – middle line + (lower line – upper line) / coefficient, where the coefficient = distance from the upper line to the middle line / distance from the upper line to the lower line.) Is this normal? The calculation results are shown in the table below:
Serial Number | Furnace Column No. | Machine Side Curvature | Furnace Column No. | Coke Side Curvature | Upper Line | Middle Line | Lower Line | Upper Line | Middle Line | Lower Line
1 | 181 | 223 | 190 | 198 | 17.5 | 181 | 227 | 208 | 209 | 7.84
2 | 182 | 222 | 196 | 197 | 10.5 | 182 | 230 | 215 | 210 | 2.6
3 | 183 | 224 | 199 | 200 | 10.12 | 183 | 228 | 208 | 204 | 5.12
4 | 184 | 215 | 185 | 186 | 12.02 | 184 | 227 | 205 | 201 | 5.88
5 | 185 | 225 | 203 | 192 | 1.54 | 185 | 223 | 205 | 206 | 7.46
6 | 186 | 218 | 196 | 196 | 8.36 | 186 | 225 | 211 | 203 | 0.36
56 | 236 | 223 | 208 | 201 | 1.36 | 236 | 224 | 215 | 194 | -9.6
57 | 237 | 213 | 198 | 197 | 5.08 | 237 | 224 | 215 | 201 | -5.26
58 | 238 | 223 | 210 | 201 | -0.64 | 238 | 219 | 219 | 202 | -10.54
59 | 239 | 215 | 201 | 195 | 1.6 | 239 | 223 | 226 | 207 | -12.92
60 | 240 | 217 | 199 | 196 | 4.98 | 240 | 229 | 226 | 206 | -11.26
61 | 241 | 212 | 194 | 201 | 11.18 | 241 | 230 | 221 | 190 | -15.8

Maximum value: 17.5
Minimum value: -0.64
Minimum negative value: -15.8